Sibling_Incest_Offenders

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Pergamon 
SIBLING 
Child Abuse & Neglect, Vol. 19, No 7, pp 811-819, 1995 
Copyright © 1995 Elsevier Science Ltd 
Printed m the USA. All rights reserved 
0145-2134/95 $9 50 + 00 
0145-2134(95)00040-2 
INCEST OFFENDERS 
NAOMI A. ADLER 
Department of Psychiatry, North Shore University Hospital-Cornell Umversity Medical College, 
Manhasset, NY, USA 
JOSEPH SCHUTZ 
Department of Applied Psychology, New York University, New York, NY, USA 
Abstract--Sibling incest is the least investigated but probably the most common form of incest. This study describes 
a predominantly Caucasian, middle-income sample of sibling incest offenders from primarily intact families. Demo- 
graphics, behavioral dysfunction, psychiatric diagnoses, history of victimization, family characteristics, and abuse 
characteristics are presented. Findings included that 92% of the offenders had a history of being physically abused, 
whereas only 8% had a history of sexual victimization. Issues of parental denial and minimization and intergenerational 
transmission of abusive patterns are discussed. Sibling incest demands further attention from clinicians and researchers 
Key Words---Incest offenders, Child sexual abuse. 
INTRODUCTION 
INTRAFAMILIAL CHILD SEXUAL abuse has been increasingly recognized as a serious 
problem over the past 20 years. Most of the professional literature has focused on fa ther- 
daughter incest, despite the assertion by many authors that sibling incest is more common 
(Cole, 1982; Finkelhor, 1979; Justice & Justice, 1979; Meiselman, 1978; Santiago, 1973). 
Sibling incest has been estimated to be at least five times more prevalent than parent-child 
incest (Canavan, Meyer, & Higgs, 1992; Cole, 1982; Finkelhor, 1980; Smith & Israel, 1987). 
However, it has come to the clinical and research attention of mental health professionals less 
frequently. 
Some authors have regarded incestuous acts between siblings as generally benign and within 
the context of normal, acceptable, sexual play or exploration (Constantine & Martinson, 1981; 
Lukianowicz, 1972; Strong & Reynolds, 1982). Yet there is a growing awareness that sibling 
incest can involve severe, repetitive, sexual abuse and lead to negative emotional sequelae for 
its victims. O'Brien (1991) found that 46% of his sample of sibling incest cases included 
penile penetration, significantly more than his cases of extrafamilial child molestation and 
sexual offenses against adults. Furthermore, he found that the mean number of acts of abuse 
for the sibling incest offenders was significantly higher than those of the other comparison 
groups. In De Jong's (1989) sample of sibling incest cases, 89% included attempted and/or 
actual vaginal penetration. Effects on victims may include lowered sexual self-esteem (Fin- 
kelhor, 1979; Laviola, 1992), sexual dysfunction as adults (Daie, Witztum, & Eleff, 1989; 
Greenland, 1958; Kubo, 1959; Magal & Winnik, 1968; Weinberg, 1955; Wiehe, 1990), revic- 
Received for publication August 22, 1994; final revision received October 27, 1994; accepted November 8, 1994 
Reprint requests should be addressed to Naomi Adler, PsyD, Chief, Family Crisis Program, Division of Child and 
Adolescent Psychiatry, Department of Psychiatry, North Shore University Hospital-Cornell University Medical Col- 
lege, 400 Community Drive, Manhasset, NY 11030. 
811 
812 N. A. Adler and J. Schutz 
timization in later life (Russell, 1986), and difficulties in establishing and maintaining relation- 
ships (Bank & Kahn, 1982; Daie, Witzum, & Eleff, 1989). 
Alpert (in press) provided a recent discussion of difficulties inherent to the study of sibling 
incest and a review of the limited sibling incest literature on issues of definition, scope, and 
effects. However, to date, there appear to have been only three studies that describe sibling 
incest offenders in detail. Becker, Kaplan, Cunningham, and Kavoussi (1986) described 22 
male, sibling incest offenders, ages 13-19, from an inner-city, low socioeconomic, primarily 
minority group, who were referred by the criminal justice system or social services. Smith 
and Israel (1987) reported on 25 low- to middle-income sibling incest families and provided 
data on the offenders, ages 9-20. O'Brien (1991) compared four adolescent male sexual 
offender groups that included 50 sibling incest offenders, 57 extrafamilial child molesters, 38 
adolescents who offended against age-peers or adults, and a mixed offender group who multiply 
abused peers, adults, and/or siblings. Almost one half of the sibling incest offenders were 
referred by social services, whereas the other groups were more likely to have been referred 
by courts. Thirty-one percent of the sibling incest offenders were from rural areas. 
Of the 19 offenders in Becker and colleagues' (1986) study who received psychiatric evalua- 
tions, 5 (26%) had no diagnosable Axis I psychiatric disorder, but 14 (74%) had one or more 
psychiatric diagnosis, including: Conduct Disorders (12); Attention Deficit Disorders (5); Drug 
Abuse (4); Adjustment Disorders (2); Social Phobias (2); Dysthymia (1); and Post Traumatic 
Stress Disorder (1). Seventy-three percent had previous arrests for sexual crimes and 50% had 
previous arrests for nonsexual crimes. Forty-one percent had engaged in nonincest paraphilic 
behaviors as well. O'Brien (1991) found that sibling incest offenders were significantly more 
likely than other offender groups to have exhibited a variety of behavioral problems associated 
with conduct disorders, including vandalism, firesetting, physical aggression, cruelty to animals, 
lying, stealing, and running away. In his sample of sibling incest offenders, half had at least 
one previous arrest for nonsexual crimes. 
Although not a causative theory, the "vampire syndrome" proposes that prior sexual victim- 
ization is a contributing factor in the etiology of sexual offending (O'Brien, 1991). Smith and 
Israel (1987) found that 52% of their sample of sibling incest offenders were victims of 
intrafamilial or extrafamilial sexual abuse. Twenty-three percent of Becker and colleagues' 
(1986) sample were sexually abused as children. O'Brien (1991) found that sibling incest 
offenders had the highest rate (42%) of prior sexual victimization compared to his other 
offender groups. He compared this finding with reports of sexual victimization in nonclinical 
male samples that have been estimated at 9% (Finkelhor, 1979) and 3% (Resnick, 1987). 
Although these figures are likely underestimates, the differences are dramatic and underscore 
the contribution of prior sexual victimization to sexual offending. O'Brien's (1991) sibling 
incest offenders were not significantly more likely to have been sexually abused by an immedi- 
ate family member compared to the extrafamilial child molesters. However, when nuclear and 
extended family members were included, two-thirds of the sibling incest offenders with histor- 
ies of sexual victimization were victimized by a relative. This was compared to one-half of 
the extrafamilial child molesters and one-fifth of the offenders against adults. 
Physical abuse has also been identified as a factor in sibling incest families. In Becker and 
colleagues' 1986 study, 14% of the sample were victims of physical abuse by their fathers. 
O'Brien (1991) found physical abuse in 61% of the families of the sibling incest offenders, 
significantly more than in the families of any other offender group. 
Sibling incest has been considered to be a reflection of various other aspects of family 
functioning as well. Justice and Justice (1979) suggested that it occurs in chaotic families, 
with passive parents who are preoccupied and pay little attention to sexual boundaries. O'Brien 
(1991) found that 47% of his sample of sibling incest offenders' families were rated by their 
therapists as severely disturbed. Extreme parental sexual behaviors have been reported in some 
sibling incest families. Smith and Israel (1987)found that approximately one-half of the 25 
Sibling incest offenders 813 
sibling incest offenders in their sample observed sexual activity between their parents or 
between one parent and another partner, or had been the victim of sexual abuse. In one-third 
of their cases, the sibling incest took place after the father sexually abused the daughter in the 
family. O'Brien (1991) found that in 22% of sibling incest families there was incestuous 
behavior in addition to the sibling abuse. Kaplan, Becker, and Martinez (1990) found that 
mothers of sibling incest offenders were significantly more frequently sexually victimized 
themselves as children than mothers of nonincest sexual offenders. Extremely repressive sexual 
attitudes among parents of sibling incest offenders have also been discussed. In Smith and 
Israel's (1987) study, 32% of the parents of sibling incest offenders were found to have rigid, 
puritanical mores and discouraged sexual expression in their children. Similarly, Meiselman 
(1978) found that seven out of eight sibling incest participants perceived their mothers to be 
puritanical and to convey that "sex is bad." 
Weinberg (1955) theorized that lack of an effective parental restraining agent contributed 
to sibling incest behavior. To explore this theory, researchers have reported on family size, 
physical or emotional availability of parents, and on the percentage of single parent families 
in sibling incest cases. Finkelhor (1980) found that girls who were sexually abused by their 
brothers were more likely to come from large families. Russell (1986) noted that 75% of her 
sibling incest victims came from families where six or more people depended on one family 
income. Of 13 sibling incest cases, Kubo (1959) found that the majority took place in fatherless 
homes where the brother assumed a parental role. In Meiselman's (1978) study, one-half of 
the fathers of the sibling incest participants were either deceased or weakened by psychosis 
or alcohol abuse. O'Brien (1991) reported that 34% of his sibling incest sample lived in single 
parent homes and 26% of the families were reconstructed. In Becker and colleagues' (1986) 
study, only 31% of the sibling incest offenders lived with both of their parents. 
The purpose of the present descriptive study was to add to the limited literature available 
on sibling incest offenders in order to heighten clinical awareness and stimulate further research. 
The sample of sibling incest offenders in this study differs from the three previous studies 
described above on several important demographic variables and therefore, it was assumed 
that important clinical and research data might emerge. 
METHOD 
This study was initiated following an influx of sibling incest cases to a hospital-based, outpatient 
psychiatric clinic's subspecialty program for family violence. Following clinical intake evalua- 
tion, the offenders and victims were assigned to individual and/or group and/or family psycho- 
therapeutic treatments. Clinical case discussions by the program's staff members led to an 
awareness of the paucity of clinical and research literature on sibling incest, as differentiated 
from the body of literature on incest in general, with its emphasis on father-daughter incest. 
The data for this study on sibling incest perpetrators was compiled from retrospective 
chart reviews of clinical intake material. Sources of information included demographic data, 
perpetrator reports, parent reports, victim reports, police reports, child protective services 
reports, school records, psychosocial evaluations, mental status examinations, and Child Behav- 
ior Checklists (Achenbach & Edelbrock, 1983). 
RESULTS 
Demographics 
The sample of sibling incest offenders in this study consisted of 12 males who were referred 
for evaluation and treatment to a hospital-based, outpatient psychiatric clinic with a specialty 
814 N. A. Adler and J. Schutz 
program for family violence. Ninety-two percent of the subjects (n = 11) were referred by 
Child Protective Services, the majority of whom were court mandated for treatment, and one 
subject was referred by his parent without the involvement of CPS. The subjects' legal involve- 
ment varied, with 58% (n = 7) being processed through Family Court only, 33% (n = 4) 
being processed through Family Court and Criminal Court, and 17% (n = 2) not being involved 
in any court proceedings. 
At the time of intake, the subjects ranged in age from 13 to 19 years old with a mean age 
of 16 and their grade level placements were from 8th through 12th grades. The sample was 
predominantly Caucasian (83%, n = 10) with only one Hispanic subject (8%) and one African 
American subject (8%) included. Eighty-three percent (n = 10) of the sample was Catholic 
and 17% (n = 2) was Jewish. All subjects were from middle or upper middle income, suburban 
families. Eighty-three percent (n = 10) of the subjects came from homes where their parents 
were married with both parents living at home and 17% (n = 2) came from one-parent homes 
with one subject's parents being divorced and one subject's parents being separated. Seventy- 
five percent (n = 9) of the subjects were living with their biological parents, whereas 25% (n 
= 3) were adopted. 
Behavioral Dysfunction 
There was no history obtained of past or current substance abuse in the sample of subjects. 
Also, there was no history of past arrests. However, there was a history of conduct disordered 
behavior, other than the incestuous sexual abuse, but not including extrafamilial sexual of- 
fending, for 58% (n = 7) of the sample. Fifty-eight percent (n = 7) of the sample had a history 
of behavior problems in school and learning problems. Only 33% (n = 4) had a prior diagnosis 
of a specific learning disability. 
Despite the fact that 58% (n = 7) of the sample was determined to have demonstrated 
conduct disordered behavior, in addition to the sexually abusive behavior, this determination 
was based on data collected from all resources available to the researchers. In contrast, when 
parents completed the Child Behavior Checklists (Achenbach & Edelbrock, 1983) on their 
sons, minimal behavioral dysfunction was noted overall. Only two subjects' profiles (17%) 
had behavior subscale scores in the clinical range. One subject's parents reported clinical range 
"delinquent" and "aggressive" behavior, "attention problems," and "withdrawn behavior." 
Another subject's parents reported clinical range "social problems" and "attention problems." 
Psychiatric Diagnoses 
Psychiatric diagnoses given to this sample based on mental status examinations and history 
were as follows: 42% (n = 5) met criteria for Conduct Disorders with one subject also 
meeting criteria for Attention Deficit Hyperactivity Disorder; 17% (n = 2) had Attention 
Deficit Hyperactivity Disorders only; and 42% (n = 5) met criteria for Depressive Disorders. 
Of note is that 75% (n = 9) of the sample had received some sort of previous intervention 
by mental health professionals, prior to and/or during their sexually abusive behavior. 
History of Victimization 
None of the subjects reported a history of being sexually victimized by an extrafamilial 
offender and only one subject (8%) reported being sexually abused by a family member (uncle) 
when he was younger. Even during the course of subsequent treatment, no further disclosures 
of sexual abuse histories were made. 
A predominant finding was the presence of a history of intrafamilial physical victimization 
for this sample of offenders, with 92% (n = 11) of the sample having a history of being 
physically abused by one or both parents. These findings were not based only on the subjects' 
Sibhng incest offenders 815 
reports, but were corroborated by parental reports and reports from social service agencies 
including child protective services. In fact, several subjects who were determined to have had 
a history of being physically abused by parentsdid not identify their own experiences as such. 
Family Characteristics 
Although 83% (n = 10) of the sample came from homes where their parents were married 
and living together, 67% (n = 8) of the cases involved significant parental marital conflict. 
Fifty-eight percent (n -- 7) of the subjects' parents had experienced one or more marital 
separation during the course of their marriage. 
Background information provided by the families revealed abuse histories in the parents' 
generation as well, including: 58% (n = 7) of the mothers of the sibling incest offenders 
reported histories of being sexually abused and 25% (n = 3) of the mothers reported histories 
of being physically abused. Only 8% (n = 1) of the fathers reported similar histories. 
When questioned about their own previous history of psychiatric/psychological intervention, 
33% (n = 4) of the mothers and 8% (n = 1) of the fathers of the sibling incest offenders 
reported some contact with mental health professionals for themselves. No subjects' parents 
reported any involvement with legal infractions previously. There were no reports of substance 
abuse history for the parents. 
Sixty-seven percent (n = 8) of the subjects came from families where there was at least 
one or more identifiable psychosocial family stressor during the time of the sibling abuse, 
including financial stress, disability, and/or illness. Forty-two percent (n = 5) of the families 
were experiencing significant financial distress and 42% (n = 5) had one parent on medical 
disability. 
Abuse Characteristics 
The sibling incest offenders in this sample were males who sexually abused their sisters 
while they were living in the same home environment. Seventy-five percent (n = 9) of the 
offenders and of the victims were biologically related to their parents and to each other, 
whereas 25% (n = 3) were adopted into the families in which they lived with 8% (one set) 
being biological siblings who were adopted into the same home. This sample came from 
families where there were two to seven children in the home with a modal number of two 
children. Eighty-three percent (n = 10) of the offenders were the oldest child in the family 
and 17% (n = 2) were the second born in the family. Fifty percent (n = 6) of the victims 
were second born children, 42% (n = 5) were third born children, and 8% (n = 1) were fifth 
born children. 
At the time of intake, the offenders ranged in age from 13 to 19 with a mean age of 16 
years old. However, at the time of onset of the sexual abuse they ranged in age from 11 to 
14 years old with a mean age of 12. At the onset of the abuse, the victims (sisters) ranged in 
age from 5 to 11 years old with a mean of 7. The age difference between offender and victim 
in this sample ranged from 2 to 7 years with a mean difference in age of 5 years. 
The duration of the sexual abuse for this sample ranged from 2 months to 72 months long 
with a mean duration of 22 months. The course of the individual cases of abuse varied with 
regard to progression and frequency. The number of discrete incidents of abuse varied as well, 
with 25% (n = 3) of the cases involving 2 - 5 incidents, 17% (n = 2) of the cases involving 
6 - 1 5 incidents, and 58% (n = 7) involving 16 or more incidents. 
Types of abuse included the following: fondling while d ressed- -100% (n = 12); fondling 
while undressed--100% (n = 12); genital exposure - -67% (n = 8); oral sex on o f f ende r - - 
83% (n = 10); oral sex on v i c t i m - - 5 8 % (n = 7); digital vaginal penet ra t ion--42% (n = 5); 
penile vaginal penet ra t ion--33% (n = 4); intercourse to e jacula t ion--25% (n = 3); and anal 
penet ra t ion--8% (n = 1). 
816 N.A. Adler and J. Schutz 
All of the offenders denied that they had used verbal threats to maintain the secrecy cloaking 
the abuse. However, 75% (n = 9) of the victims reported that they had been verbally threatened 
to maintain silence. Ninety-two percent (n = 11) of the offenders reported that no violence 
was involved in their abuse and 8%, or one subject, reported that he had been physically 
violent as well as sexually abusive. The victims' reports matched the offenders' reports on 
this variable. 
The sibling abuse in this sample was disclosed in various ways, including: 8% (n = 1) 
victim to parent; 75% (n = 9) victim to other, including teacher and/or therapist; and 17% (n 
= 2) parent observation of abuse. Not one offender disclosed his own abusive behavior, despite 
the fact that 75% (n = 9) had been in some form of mental health treatment previously. 
Following disclosure, 8% (one subject) of the offenders made a full acknowledgement, 75% 
(n = 9) made a partial acknowledgement, and 17% (n = 2) completely denied the accusations. 
It is important to note that in 58% (n = 7) of these cases, there had been prior disclosure of 
the sibling abuse either through parent observation or victim to parent disclosure. However, 
the parental interventions at that time, which included yelling, lectures on appropriate behavior, 
and telling the siblings to stay away from each other, were not effective and the abuse continued. 
Based on intake material and subsequent therapeutic treatments, it was determined that the 
offenders of sibling incest in this sample were not involved in other sexual offending and/or 
paraphilic behavior. 
DISCUSSION 
Review of the literature revealed only three previous substantial empirical descriptions of 
samples limited to sibling incest offenders, including Becker and colleagues (1986), Smith 
and Israel (1987), and O'Brien (1991). A comparison of the findings on commonly investigated 
variables from these three previous studies and this study can be found in Table 1. 
Although the current study suffers from the lack of a comparison group, as do two of the 
three other mentioned studies, it contributes to the limited empirical literature to date on sibling 
incest offenders because it focuses on a demographic sample that has not been described 
previously. This sample of sibling incest offenders came from middle to upper middle class, 
suburban, primarily Caucasian families, of whom 83% (n = 10) had both parents married to 
each other and living in the home. There was no prior involvement with the juvenile justice 
system in this sample, as compared to 50% of the sample's involvement in Becker and 
colleagues (1986) and 41% of the sample's involvement in O'Brien (1991). Clearly, these 
findings challenge the possible assumption that the potential for sibling incest does not exist 
in these types of family environments that, superficially, appear to be intact and functional. 
General risk factors for incest such as physical absence of a parent and low socioeconomic 
circumstances (Finkelhor, 1979) were not relevant for this sample. Other potential risk factors 
that did exist for this sample and that require further investigation include: family stress due 
to financial distress in a middle to upper middle class family; parental illness/disability; marital 
conflict; and pervasive family patterns of abuse. 
In contrast to high percentages of prior sexual victimization of the offenders that has been 
found for juvenile and adolescent sexual offenders in general and sibling incest offenders 
specifically (i.e., Becker et al., 1986--23%; Smith & Israel, 1987--52%; O'Brien, 1991-- 
42%), only one offender in this sample (8%) had a similar history. It is unlikely that this 
finding is due to denial and/or minimization because clinicians sensitive to this issue treated 
the offenders subsequent to intake with no further disclosures made. However, the finding of 
high percentages of sexual victimization histories for the parents of the offenders in this sample, 
was consistent with the findings of previous studies (see Table 1). Furthermore, Kaplan and 
colleagues (1990) found that 34% of the mothers of adolescent incest perpetrators in their 
Sibling incest offenders 817 
study had histories of sexualvictimization, a significantly higher percentage than the mothers 
of nonincest perpetrators. O'Brien (1991) discussed that there seems to be support for the 
intergenerational transmission hypothesis with regard to the etiology of sibling incest, perhaps 
related to interpersonal boundary violation patterns, but that the mechanism of transmission 
remains unclear. The family intergenerational transmission may not be specific to sexual abuse, 
but rather to abusive patterns in general that may manifest in sexual, physical, and/or emotional 
abuse. The most glaring finding in the current study was that 92% (n = 11) of the sibling 
incest offenders had a history of being physically abused by one or both parents. This is 
consistent with O'Brien's (1991) finding that 61% of his sample of sibling incest offenders 
had physical abuse in their families, although it was unclear as to whether or not the sibling 
incest offenders had been direct victims. The risk for manifestation of pervasive family abusive 
patterns in sibling incest may peak when a victimized child becomes sexually aware and 
interested. This is consistent with the finding in this study that the age of onset of the sibling 
incest was when the offenders ranged from 11 to 14 years old. For a sexually abused child 
or a child who grows up in a sexualized family climate, such as the environment described 
by Smith and Israel (1987), this phase of development may occur prematurely. In Smith and 
Israel's (1987) study, where 52% of the offenders had been sexually abused themselves, the 
offending behavior began as young as 9 years old. 
Parental denial and minimization in relation to sibling incest, perhaps as a result of their 
own histories of victimization, have been discussed by Kaplan and colleagues (1990) and 
O'Brien (1991). The current study's finding that 58% (n = 7) of the sibling incest cases had been 
exposed previously but continued following ineffective parental intervention, lends support to 
the pervasiveness of parental denial and minimization. Furthermore, denial and minimization 
were clearly evident by the fact that in addition to the sexually abusive behavior, 42% (n = 
Table 1. Comparison of Descriptive Data on Sibling Incest Samples 
Becker et al. Smith & Israel O'Brien Adler & Schutz 
(1986) (1987) (1991) (1995) 
Sample Size n = 22 n = 25 n = 5(1 n = 12 
Offender Age 13-18 9 - 20 12-19 At intake 13-19 
= 14.8 • = 13.2 x = 15 Y = 16 
At onset 11-14 
Offender Gender 100% male 80% male 100% male 100% male 
20% female 
Victim Age 3-13 76% < 9 5-13 
• =9.1 ? f = 7 
Victim Gender 89% female 100% female 
11% male 
SES inner-city low SES primarily 31% rural middle-upper 
low-middle suburban 
Race 14% Caucasian 96% Caucasian 90% Caucasian 83% Caucasian 
32% Hispanic 4% Hispanic 4% NaUve American 8% Hispanic 
54% African American 6% African American 8% African American 
23% 52% 42% 8% Offender's Sexual 
Victimization 
Offender' s 14% 
Physical 
Victimization 
Other Incest in 
Home 
Parents' Sexual 30% 
Victimization 
Parents' Physical 27% 
Victimization 
61%~ 92% 
32% 22% 
72% 36% M 
10% F 
0% 
58% M 
8% F 
25% M 
8% F 
a O'Brien (1991) reported 61% physical abuse in family, but it was not clear if sibling incest offenders were direct 
victims of physical abuse. 
818 N.A. Adler and J. Schutz 
5) of this study's sample of offenders were diagnosed as having conduct disorders and 58% 
(n = 7) were found to have demonstrated behavior problems in school. However, parental 
reports on their sons' behavior using the Achenbach Child Behavior Checklist indicated mini- 
mal behavioral dysfunction overall. This is in contrast to Johnson's (1993) work on children 
who molest (not limited to intrafamilial offending), in which she described finding parental/ 
caretaker Achenbach Child Behavior Checklist scores that were pervasively clinically signifi- 
cant. 
The current study's findings, taken together with the limited previous work in this area, 
indicate that sibling incest is a form of intrafamilial abuse that demands further attention from 
clinicians and researchers. Certain sexual interactions between siblings can be mutual and 
within the context of normal exploration and play, but they can also be seriously abusive. 
Factors that underscore the severity of the abuse in this study's sample include a mean age 
difference of five years between offender and victim, the finding that 58% (n = 7) of the cases 
involved 16 or more incidents, the high incidence of oral sex and vaginal penetration, a mean 
duration of 22 months, and a high frequency of verbal threats used to maintain secrecy. It is 
likely that the majority of sibling incest is not disclosed. Intervention is complicated by the 
fact that even when it is disclosed to parents, ineffective intervention may take place and the 
abusive behavior may continue. Denial and minimization contribute to this possibility, as does 
the myth that all sibling sexual interactions are benign and in the course of normal development. 
Sibling incest may be just the "tip of the iceberg" with regard to the family dysfunction and 
intergenerational patterns of abuse from which it likely stems. Society's contribution to denial 
and minimization with regard to the seriousness of sibling incest is reflected by the minimal 
involvement of Criminal Court in these cases. Furthermore, Child Protective Services may not 
even get involved in sibling incest cases once they are disclosed, even if they are reported, if 
parents are not found to be neglectful. In many of the cases described in this study, once 
parents brought their children to the mental health agency, their child protective services cases 
were closed. Only when the clinicians reported further neglectful or physically abusive behavior 
on the part of the parents, were some of the cases reopened. 
The results of this study lend strong support to O'Brien's (1991) conclusions that sibling 
incest must be addressed more seriously by judicial, child protection, and mental health systems 
on prevention and intervention levels. Prevention of sibling incest is likely to stem from 
eradication of the myth that it is benign and from effective prevention work with families at 
risk for abusive patterns in general. Intervention must include individual and group therapy 
specific to the sexual abuse for the offender and victim as well as therapeutic treatment of the 
families (O'Brien, 1991). This may need to include individual work with the parents on their 
own histories of victimization. Clearly, the extent of the required therapeutic intervention is 
daunting and therefore, it requires a multi-system commitment to its necessity. 
Although it is clear that sibling incest must be addressed, the results of this study must be 
supplemented by future research that investigates etiological variables, including the offenders' 
histories of being neglected, physically abused, sexually abused, and/or emotionally abused. 
Familial factors such as extent of supervision and/or parental restraint, abusive patterns in 
general, and other psychosocial stressors need to be studied. Studies should include larger 
samples, and use appropriate comparison groups and research measures for the offender, victim, 
and family that are reliable and valid. Furthermore, the effectiveness of treatment interventions 
must be documented with outcome research. 
Acknowledgement--The authors wish to thank David Merlob for his assistance with data collection. 
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R~sum6----L'inceste entre fr6res et soeurs fait rarement l'objet de recherches bien qu'il soit possiblement parmi les 
plus fr6quents types d'inceste. L'article rapporte une 6tude sur des agresseurs issus de families essentiellement intactes, 
principalement de race blanche et de milieu socio-6conomique moyen. On commente les aspects d6mographiques, les 
comportements dysfontionnels, les diagnostiques phychiatriques, ies ant6c6dents des victimes, les caract6ristiques 
familiales et les caract6ristiques de i'agression. Les auteurs concluent que 92 p.c. des agresseurs avaient eux-m6mes 
6t6 abus6s physiquement alors que seulement 8 p.c. des agresseurs avaient 6t6 abus6s sexuellement. La n6gation des 
parents, la minimisation ainsi que la transmission d'une g6n6ration h l'antre sont discut6s. On recommande que les 
cliniciens et les chercheurs poussent plus loin leurs connaissances de cette probl6matique. 
Resumen--El incesto entre hermanos es uno de los menos investigados y probablemente de las formas mils comunes 
de incesto. Este estudio describe una muestra perdominantemente cauc~isica, clase media de perpetradores de incesto 
entre hermanos de familias mayormente intactas. Se presentan caracteristicas demogr:ificas, disfunci6n conductual, 
diagn6stico psiqui~itrico, historia de victimizaci6n, familiares y del abuso. Los resultados demuestran que 92% de los 
perpetradores tenian una historia de haber sido ffsicamente abusados, mientras que solo un 8% tenia una histona de 
victimizaci6n sexual. Se discuten los aspectos de negaci6n parental y minimizaci6n asf como transmisi6n intergeneraci- 
onal de patrones abusivos. El incesto entre hermanos demanda mas atenci6n de los clfnicos e investigadores.