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Understanding Sibling Incest

source: John Pesciallo


The issue of child abuse and neglect is an increasing social concern. Consequently the role of social workers is more pronounced and involved; especially that of a Child Protective Services worker. Perhaps one of the most trying issues for the worker is that of sibling-to- sibling sexual abuse. (I use the term “sibling-to-sibling” because some of the literature I have read categorizes father-daughter incest as sibling incest; herein referred to simply as sibling incest.) In this article, when sibling incest is mentioned it is referring generally to older brother abuse of a younger sister. Recognizing the risk factors, understanding the causes, and making an assessment, can be challenging. Many sibling offenders are found to have a history of abuses suffered themselves. While this does not excuse their behavior, it may overlook a deeper and more volatile issue. Even though sibling offenders may be viewed as having suffered from abuse themselves prior to their abusing, the sibling abuse they inflict may stem from their own unmet needs more than from the fact of having been abused themselves.

Understanding Sibling Incest

Child Abuse and Neglect cases are mentioned more frequently lately in the media. In the last few months in Oregon alone there has been several articles published. One fairly recent article is by Kate Taylor in the April 23, 2020 issue of “The Oregonian” (The Oregonian [Online]):

Child-abuse cases jump, agency says:

Instances of abuse and neglect climb 17 percent in 1997, and deaths of children also are up.

In 1996, there was nationally an average of 44 reports of child maltreatment per 1,000 children (NCCAN [Online]). In 1994, there were 16 confirmed victims for every 1,000 U.S. children (NCPCA, 1995, [Online]).

Of the various forms of child abuse and neglect, sibling-to-sibling physical sexual abuse may be one of the most difficult forms of sibling physical abuse for social workers to deal with. Defining sibling physical sexual abuse can be a dilemma in and of itself. Definitions tend to vary according to the institution or individual involved with victims of sibling incest. One definition of sibling incest is: sexual interaction beyond age-appropriate exploration such that “older siblings, who differ significantly in age or by virtue of their power and resources, may also be considered abusive” (Tower, 1996, p. 134). An alternative definition of sibling physical sexual abuse is… physical sexual activity or touching of a child in a sexual way by a family member (Mellody, 1989, p. 149). Child Protective Service (CPS) of Washington describes sexual abuse as “Using a child for sex acts, pornographic pictures, prostitution, or other types of sexual activity” (DSHS; Parents Guide to CPS, 1990, p. 2). These definitions, while aptly expressing inappropriate sexual behavior, fail to recognize the complicated nature of offenders or the causes of their behavior. Like so many other human problems, multiple factors are involved in the occurrence of sibling sexual abuse. One probable cause for sibling-to-sibling incest is unmet needs because of dysfunctional parents or parenting.

Sibling-incest may sound like a terrible thing and be hard to understand how it could occur, and it is, but one of the best ways to deal with it is to understand it. Several risk factors within the family may lead to sibling sexual abuse; economic / financial problems, marital discord, parent-sibling rivalry, drugs and alcohol abuse, illness, or poor intrafamilial communication to name a few. The list could go on-and-on. The resulting discord within a family has adverse effects upon the children. These effects may be conceptualized in the form of unmet need(s) resulting in sibling sexual abuse rather than prior sexual abuse of the perpetrator within the family. In a review of earlier data on sexual victimization experiences of perpetrators, O’Brien (1991), found that only a minority of sibling perpetrators had experienced sexual abuse within the family. “However, it is also important to recognize that many, many children with unmet needs due to family dysfunction do not seek to fulfill their need through abuse of another (Olson, 1998).

If a disturbing conflict within the family continues unresolved for a significant length of time, children may adversely adapt to this tension. Instead of coping appropriately, children may cope inappropriately. One form of inappropriate coping is sibling incest. For siblings close to the same age, incest may merely be sexual exploration that is a part of normal development but socially unacceptable or undesired. However, when there is coercion or a significant age difference, then it is considered abuse. Generally, the difference of five or more years would constitute abuse by the older child (even if the younger child were willing). Anytime an older sibling manipulates a younger child into sexual behavior that is not age appropriate or socially acceptable, it is sexual abuse (SOWK-464 class notes, 4-14-98). However, families that form extreme stress in and outside of the family may have reduced coping mechanisms ([No author] Journal of Mental Health Counseling, 1997).

So, why would the older sibling behave incestuously with the younger sibling? The answer to this can be found by considering the needs of the offender. Justice & Justice (1979) have described incestuous families as dysfunctional and disorganized, with their members lacking role definition (Quoted in Ascherman & Safier, 1990). Many other descriptions have been given by various authors in their attempt to understand incest as a symptom of family dysfunction. Obviously family dysfunction is a risk factor for abuse, but the dynamics between risk factors and incest involving unmet needs has largely been ignored in literature.

When a child’s needs are unmet, he/she may meet those needs in socially unacceptable means with sibling abuse being one of those means. Children, including adolescents, need a certain amount of physical affection from their parents (Strong, DeVault, & Sayad, 1996). The amount of physical affection affects children’s emotional and sexual health (p. 141). If a child is distanced from one parent, then there is an unmet need for intimacy with that parent. The child then copes with this discord the best he can. In cases where the father has favored the son’s younger sister and the mother has favored the son, the son may attempt to meet his unmet needs from his father by being involved with the father’s favored daughter. His motivation may be to satisfy an important emotional need (Finkelhor, 1986, p. 60). This involvement may then progress into incest. However, this doesn’t necessarily mean that he is an aggressor. “Both may willingly engage in the behavioral… attempt to cope with unmet needs” (Loredo, 1982, quoted in Ascherman & Safier, 1990). Although there may be a temptation by workers to reduce the occurrence of incest to a specific set of circumstance some cases will demonstrate an overlapping of risk factors that coalesce into incest (Ascherman & Safier, 1990). It is therefor important that as a social worker assesses the risk factors and dynamics occurring within the family not to generalize his/her findings to indicate a specific form of abuse.

Ascherman & Safier (1990) recommend that assessment of incest cases consider the kind of incest that has occurred in relation to its context and the broad intrafamilial dynamics and psychopathologies. While a case may have several contributing factors that are in common with other sibling abuse cases, no single factor alone can provide adequate explanation for the abuse. This situation is quite often further complicated by the reactions of other family members: father, mother, other siblings, extended family members, and friends. All these interact to form a complex web of interactions. Their role within the family dynamics can have a decisive influence on the offending sibling.

According to William Glasser, M.D. (1998), we have four psychological needs: love and belonging, power, freedom, and fun. These needs are genetically programmed and by the genius of nature, we have the ability to meet our needs before we know what or why we are doing it. Even if we do knot know why we are doing it, we still remember feeling good (p. 28). This may explain how a sixteen-year-old becomes incestuously involved with his younger sister. He is unhappy, has an unmet need, and finds that he enjoys playing “house” with his little sister. The dysfunctional dynamics of the family contributes to his unmet needs and his opportunity to meet them with his little sister. If little sister has similar unmet needs, then the incestuous relationship may be mutually rewarding.

Assessing a potential case of sibling incest involves critiquing not only family dynamics but also the factors motivating those dynamics. After conducting a family assessment, noting the dynamics of family members, and the cognitive-behavioral dynamics of the client (offender), this assessment is further evaluated for motivational factors. In a study of juvenile sex offenders Ryan et al. (1987) commented that losses [and thus a need] of nurturing or parental relationships during infancy or early childhood may be a factor. In fitting with Glasser’s four psychological needs, this would represent a need for “love and belonging” on the part of this client. Treatment could then be directed towards meeting that need. The philosophy behind this approach is that by meeting his needs “appropriately,” the “inappropriate” meeting of those needs will be reduced. Finkelhor and Browne (1985) have suggested that abused children learn to meet their needs through sexual behavior (No author. Quoted in Journal of Mental Health Counseling, 1997). One of the key issues then for the client is to understand, accept, and recognize these errors in thinking in meeting their needs (Ryan, et al., 1987). It is important to assess these needs because assessing the events of sibling incest without assessing motivational factors is like a doctor treating the symptoms without treating the cause of the symptoms. If a sibling offender learns to recognize the unmet need and learns an effective and appropriate substitute for incest, then the incest may be avoided.

When assessing a family for a potential occurrence of sibling incest, a common risk factor may be overlooked. Although it may seem overly simple, an unhappy family life is a significant risk factor. Finkelhor et al. (1990) found that compared to 1) lived w/o a natural parent, 2) few friends, or 3) inadequate sex education, having an “unhappy family life” was the most prevalent risk factor for both men (35% victimized) and women (60% victimized) for the occurrence of childhood sexual abuse. Such a simple need, yet frequently unmet “or perhaps not so simple” (Olson, 1998).

In a study by Worling (1995), of 90 adolescent male sex offenders committing physical acts, he stated that: “children who live with abusive and rejecting parents may turn to each other for comfort, nurturance, and support” and the onset of puberty places the children at risk. This suggests that a male sibling that begins puberty and has unmet needs for comfort, nurturance, and support may turn to his sister to meet these needs. She may be a willing partner in order to get her needs met. This occurs because they both live with the same pair of dysfunctional parents. According to “blockage” theory, “sex offenders are somehow blocked in their ability to get their sexual and emotional needs met in appropriate peer relationships and therefore choose alternative victimizing avenues for need fulfillment” (O’ Brien, 1991, p. 84).

Worling (1995) also noted that the comparison group of non sibling-incest adolescent offenders and those of the sibling-incest group did not differ substantively in terms of depression, self-esteem, hostility, peer popularity, aggression, or physical parental punishment and negative family relationships. However, the parents of the sibling-incest offenders were reported to be significantly more dysfunctional and abusive, which fits with the findings of O’Brien (1991). Children need parents that are functional and non-abusive. When parents are dysfunctional and abusive it places the children at risk for sibling-incest in brother-sister families. It is therefore important to consider parental factors when screening for sibling abuse. Worling’s conclusion was that verbal, emotional, and physical violence combined with a history of sexual victimization places the children at risk for sibling-incest (Worling, 1995, p. 641).

Social Workers working with abused children need to be familiar with the process of screening reporters (those reporting an abuse) and clients of child abuse in order to gather data effectively. Conducting an interview centered on sibling-incest would require a working understanding of what is normal and what is abnormal child sex acts. Three main categories for evaluating sibling incest are 1) experimentation, 2) exploitation, and 3) abuse (Abrams, 1993). An act considered “experimentation” might be young children close in age, size, and cognitive level. An act of “exploitation” might be if their behavior has been repudiated but the frequency of the behavior has not reduced. An example of “abuse” could be a sex act where there is considerable age or developmental difference between the two children. Before ending the questioning of the client it is important to ask: “Has anyone else done this to you?” because the child may have been abused by more than one individual. He or she may have learned the behavior from another. This information can then be used for assessment and treatment planning (SOWK-464, class notes, 4/28/98).

I believe the family setting is the most viable factor for positive growth. In a clinical follow-up by Lewis, D., et al. (1994), of 97 formerly incarcerated male delinquents, the only placement of released incarcerated violent Juvenile delinquents that was associated with positive outcomes, was placement back home regardless of the home environment. The authors concluded that; 1) even in the most dysfunctional and abusive of homes there is at least one family member who cares about the returning youth, and 2) even though children returned to home are exposed to other delinquent and criminal individuals, they are also exposed to law- abiding people who are role models of alternative modes of coping (p. 527).

Sibling-incest cases can be multifaceted, meaning that more than one or two dynamics are or have occurred that contribute to the abuse. Therefore, it is important to have a comprehensive protocol to use when screening or assessing sibling-incest cases. Smith and Israel (1987) have suggested a list of categories for obtaining data during the investigative intake process:

1. Nature and duration of sexual contact.

2. Where sexual contact occurred.

3. Who knew about the sibling sexual contact.

4. Whom did the victim tell.

5. History of prior sexual abuse of either victim or perpetrator.

6. Prior history of sexual abuse of parents.

7. Possible sexual activity between parent and child.

8. Significant role reassignment in family.

9. Quality of marital relationship.

10. Parenting responsibilities.

11. Sexual boundaries in the home; restrictive or flexible.

12. Ability of parents to protect children in the future.

Personally, I would add two more to this list:

13. What unmet needs do the parents have.

14. What unmet needs do the children have.

Smith and Israel, like so many other authors, use the term “perpetrator” to label the child. A label can be a self-fulfilling prophesy, or stigmatize the client, so a more neutral term is desired. Mehr (1995) has suggested than when an individual is described by label specific terminology (“role characteristics”), the person often is perceived as belonging to the class of people given that role label.” This individual may confirm the label by considering himself in those terms (95). Not only is sibling-incest complicated, even the terminology used can be a concern.



Sibling incest is a complex issue that calls for an awareness that the dynamics of one case may not transfer to another similar case. Therefore, “Evaluators of incest cases should note the kind of incest, its context, the ages of participants, the family dynamics, and the individual psychopathology of family members so as to adequately understand the incest and effectively plan treatment” (Ascherman & Safier, 1990). The “needs” of participants is but one aspect of family dynamics to consider among many, but an important one. The broader a picture a social worker has (within reason) of a sibling incest case or any abuse case, the better he or she is equipped to intervene and assess that case. Although sibling incest offenders may be known to have suffered from abuse themselves prior to their abusing, the sibling abuse they inflict may, in part at least, stem from their own unmet needs as much as or more than from the fact of having been abused themselves.


Abrams, H. (1993). Evaluating sibling incest. Child Services District, Walla Walla College, Class handout, SOWK-464.

Ascherman, L. & Safier, E. (1990, Summer). Sibling incest: A consequence of individual and family dysfunction. Bulletin of the Menninger Clinic, Vol. 54(3), pp. 311-323.

Finkelhor, D. (1986). Sexual abuse: Beyond the family systems approach. National Center for Child Abuse and Neglect. Hawthorn Press.

Finkelhor, D., et al. (1990). Sexual abuse in a national survey of adult men and women: Prevalence, characteristics, and risk factors. Child Abuse & Neglect, Vol. 14, pp. 19-28.

Glasser, W. (1998). Choice Theory. Harper Collins.

Journal of Mental Health Counseling (1997). Adolescent sex offenders: Identification and intervention strategies. Vol. 19(4): pp. 336-349.

Lewis, D., et al. (1994). A clinical follow-up of delinquent males: Ignored vulnerabilities, unmet needs, and the perpetuation of violence. Journal of the American Academy of Child Adolescence Psychiatry, 33(4), pp. 518-528.

Mehr, J., (1995). Human services: Concepts and Intervention strategies (6th ed.). Allyn and Bacon.

Mellody, P. (1989). Facing codependence: What it is, where it comes from, how it sabotages our lives. New York, N.Y. HarperCollins Publishers.

National Clearinghouse on Child Abuse and Neglect Information (1998). National child abuse and neglect statistical fact sheet [Online]. Available: stats.htm [1998, April 1].

NCPCA (1995, April). Child abuse and neglect statistics from the national committee to prevent child abuse [Online]. Available: [1998, May 1].

O’Brien, M. (1991). Taking sibling incest seriously. In M. Patton (Ed.), Family sexual abuse: Frontline research and evaluation, pp. 75-92.

Ryan, G. (1987). Juvenile sex offenders: Development and correction. Child Abuse and Neglect, Vol. 11: pp. 385-395.

Smith, H. & Israel, E. (1987). Sibling incest: A study of the Dynamics of 25 cases. Child Abuse and Neglect. Vol. 11, pp. 101-108.

Strong, B., DeVault, C. & Sayad, B. (1996). Core Concepts in Human Sexuality. Mountain View, CA. Mayfield.

Taylor, K. “Child-abuse cases jump, agency says: Instances of abuse and neglect climb 17 percent in 1997, and deaths of children also are up” [Online]. Oregonian Oregon Live: News 23 April 1998. Available: [1998, May 2].

Tower, C. (1996). Child abuse and neglect (3rd ed.). Allyn and Bacon. p. 137-189.

Washington State Department of Social and Health Services / (1990). DSHS Parent’s guide to child protective services (CPS).

Worling, J. (1995, May). Adolescent sibling-incest offenders: Differences in family and individual functioning when compared to adolescent non-sibling sex offenders. Child Abuse and Neglect. Vol. 19(5): pp. 633-643.

© Copyright 1998 – John Pesciallo – BSW Student


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