Sibling sexual abuse

ACSSA Research Summary No. 3 – October 2012

What is sibling sexual abuse?

Exactly what constitutes sibling3 sexual abuse is a matter of contention and confusion for abused siblings, abusing siblings, family members and professionals (Hatch & Hayman-White, 2001; Pratt et al., 2010; Rowntree, 2007). There are some indicators that may be useful in the identification of sibling sexual abuse for parents and professionals, however they are marked by inconsistencies between studies and cover cultural, therapeutic and legal frameworks. Krienert and Walsh (2011) suggested that definitional inconsistencies create fractured knowledge that restricts policy-makers and therapeutic agents "from making informed decisions in the interest of reducing the prevalence and scope of sibling sexual abuse" (p. 350).

Following is a discussion of the most debated and significant aspects related to defining sibling sexual abuse contained in the reviewed literature.

Age difference between the abused and the abuser

One of the most widely cited research studies into childhood sexual abuse was conducted by Finkelhor (1980) who based his definition of sexual abuse between children on differences in age (Rayment & Owen, 1999). The age gap that constituted abuse was 5 years or more. There is still debate around how big the age difference is before mutuality gives way to coercion but much of the literature indicates between 2-5 years difference (Carlson et al., 2006).

Many current studies have found that children with problematic sexual behaviours are usually older than their victims (Krienert & Walsh, 2011; Monahan, 2010). In an Australian clinical sample study of 17 young women abused by their siblings, Welfare (2010) found that the average age difference was 4.18 years. In another Australian study based on outcomes for the abusing child, Rayment-Hugh and Nisbet (2003) defined a child victim as a person under 13 years of age, and at least 3 years younger than their abuser. Monahan (2010) echoed this age difference and distinguishes consensual sex play from coercive sibling sexual assault on a difference of more than 3 years.

Although age difference may be a good indicator in coercive sexual contact between children it is dangerous to ignore the fact that there can also be coercion between children of a similar age and McVeigh (2003) warned that age should not be the only indicator. If the abusing child is physically larger than the victim they may use this strength to physically intimidate their victim, or they may just rely on threats.

Further, as cited in Hatch and Hayman-White (2001), age is of little consequence when sibling victims are chosen on the basis of their vulnerability, such as isolation, parental neglect, emotional dependence, smaller physicality or disability. A large-scale national US study of police reports of sibling sexual abuse noted that verbal coercion and/or manipulation were common tactics used by siblings (Krienert & Walsh, 2011).

Coercion and violence

Although violence is not always present in sibling sexual abuse, coercion is certainly considered an identifying factor. The same national study cited above found that the use of weapons in sibling sexual abuse, although common in their national sample, usually indicated the abusive sibling used their hands and feet to subdue their victim (Krienert & Walsh, 2011). The most common forms of coercion found in sibling sexual abuse incidents were verbal coercion, threats and bribery/trickery (Carlson et al., 2006; Hatch & Hayman-White, 2001).

In one case study, a young girl was "tricked" into sexual acts by her brother who originally offered physical comfort through hugs and other non-sexual physical contact and eventually escalated the physical contact to include sexual acts (Ballantine, 2012). He did not need to coerce her more forcefully as she was vulnerable due to her "harsh family environment … and the family's low opinion of her" (p. 60) which had left her with poor self esteem and desire for acceptance.

However there are also studies that found child sexual abuse can involve physical coercion and an escalation in forced sexual acts (Paine & Hansen, 2002). For example, the abuse may begin with unwanted sexual comments to unwanted genital touching and evolve to forced penetration (Carlson et al., 2006).

In a study based on a sample of 41 victim/survivors of sibling sexual abuse - both men and women - 68% reported coercion, threats and/or bribery, 10% were threatened with physical violence and 5% indicated "threats to withhold privilege or offers of money or gifts" (Carlson et al., 2006, p. 27). Another study with 43 victim/survivors of sibling sexual abuse found 25% had been coerced through physical force, 11% with verbal threats, 32% with bribery/trickery and the remaining had a combination of physical/verbal, physical/bribery and verbal/bribery coercive tactics used against them (Hatch & Hayman-White, 2001).

Developmentally inappropriate sexual behaviour

Developmentally inappropriate behaviour and problematic sexual behaviours can be distinguished as two categories, although there is cause to consider some overlap between them. For the purpose of this paper they will be separated and problematic sexual behaviour will be presented in the section below. Although a distinction is being made, both can be present in a child who has been victimised in the past. A child who has been abused by a sibling may present developmentally inappropriate behaviour and problematic sexual behaviour, and a child who displays abusive behaviours toward their sibling/s may be acting out either developmentally inappropriate behaviour or problematic sexual behaviour.

Developmentally inappropriate sexual behaviour refers to behaviour that is not in line with a child's physical and mental development. It can be a result of a family environment that allows exposure to highly sexual language and media or is extremely tolerant to sexual contact and activity (Hatch, 2005).

An Australian Crime Commission report (O'Brien, 2008) cautioned that more research is needed into child sexuality in order to understand what is and is not developmentally inappropriate. However any definitional categories contain the risk of pathologising childhood sexuality by determining too stringent guidelines as to which behaviours are appropriate for which age groups (O'Brien, 2008). O'Brien warned that "researchers need to resist the apparent comfort offered by fixed definitions or exhaustive lists" (p. 8). Nonetheless, some broad definitions are included in the report and are presented below in Table 1.

Problematic sexual behaviours

Unlike the discussion on developmentally inappropriate/appropriate behaviours, a discussion of problematic sexual behaviours concerns the use of coercion, intimidation and lack of consent (McVeigh, 2003). There is an element of secrecy in sibling sexual abuse that is enforced by the child with problematic sexual behaviour - as well as a power dynamic (McVeigh, 2003). The field of study related to child and adolescent problematic sexual behaviours is becoming more relevant as the high prevalence of child sexual abuse becomes known and issues of how to respond to children who display problematic sexual behaviours are discussed. Two recent reports by the Australian Crime Commission (O'Brien, (2008; 2010) highlighted the importance of separating the sexually abusive behaviours from the child in order that abusive siblings are given an opportunity to change their behaviours (see Box 1). This, however, must be balanced with the needs of the victim/survivor, and should not function to minimise their pain and suffering (O'Brien, 2010).

Table 1a: Developmentally based sexual behaviours - inappropriate, ages 0-18
Age group Developmentally inappropriate sexual behaviours
0-5 Years of age Curiosity about sexual behaviour becomes an obsessive preoccupation

Exploration becomes re-enactment of specific adult activity

Behaviour involves injury to self

Children's behaviour involves coercion, threats, secrecy, violence and aggression

6-10 Years of age Sexual penetration

Genital kissing

Oral copulation

Simulated intercourse

11-12 Years of age Any sexual play which involves children younger than themselves.
13-18 Years of age Compulsive masturbation

Attempt to touch or expose other's genitals - especially without permission

Sexual contact with animals and younger children

Using sexual themes to degrade others or themselves

Chronic preoccupation with sex and pornography

Table 1b: Developmentally based sexual behaviours - appropriate, ages 0-18
Age group Developmentally appropriate sexual behaviours
0-5 Years of age Engaging in exploratory touch

Looking at themselves and others

6-10 Years of age Playing games as a form of sexual exploration (playing doctors)

Telling dirty jokes

Using dirty words

Showing interest in changes in their bodies

11 & 12 Years of age Peer related sexual activity

Sexual activity with same gender


Sources: Pratt et al. (2010); McVeigh (2003; p. 116); Araji (cited in O'Brien, 2008, p. 8).

Children who display problematic sexual behaviours towards their siblings may be acting out trauma as a result of having being sexually victimised themselves (Rayment-McHugh & Nisbet, 2003). When this is the case, "children and young people with sexualised behaviours confound understandings of ‘victim' and ‘offender' as mutually exclusive categories" (O'Brien, 2010, p. 5).

Certain family environments may have a negative effect on children that lead them to enact problematic sexual behaviours against their siblings. Exposure to pornography or other sexually explicit material can lead to children "copying" the behaviours they have seen. Similarly, permissive boundaries around sexual language and sexual behaviour may also have an effect (Hatch, 2005). Based on case studies of sibling sexual assault victims, one researcher stated that a patriarchal environment, which relies on traditional values, may create the context for sibling sexual abuse (Ballantine, 2012).

The terminology used to describe the behaviours of children who sexually transgress against their peers or family members is a difficult but important consideration. In order for the child who displays problematic sexual behaviours to separate the abusive act from who they are, it is important to use language that separates the abusive behaviour from the child. For example, terms such as "perpetrator" and "offender" label the child. Conversely, using terms such as "abusive behaviour" or "child who displays problematic sexual behaviour" lessens the stigma and offers potential to change the behaviour (O'Brien, 2010).

Availability and duration

Although duration of abuse is not strictly a definitional aspect of sibling sexual abuse, studies have indicated that duration is a feature because siblings live together and the abusing sibling has access to their victim (Hatch, 2005). Hatch pointed out that the close proximity of siblings also marks sibling sexual abuse possibly as an opportunistic crime - indicating that there is little difference between those who abuse siblings and non-siblings except for sibling availability (Welfare, 2008).

Women's Health Statewide (2005) conducted a study of 18 women who had been abused by their brothers and found that the longest period of abuse lasted 10 years, and the least for 1 year. The average abuse period was 5 years. Welfare (2010) found in her sample of 17 women abused by their siblings at different ages, but predominantly early adolescence, that the average length of time abused was 4.76 years and that the abuse ceased around the time the abused sibling reached adolescence.

In one study that included 41 victim/survivors of sibling sexual abuse, the average duration of abuse was 6 years (Carlson et al., 2006). The abuse ceased when:

  • the victim left home (10%);
  • the child with problematic sexual behaviour left home (25%);
  • the child with problematic sexual behaviour either started a romantic relationship (with a non-family member) or began abusing someone else (10%);
  • the abuse ceased for unknown reasons (30%);
  • the abuse ceased because it was discovered (7.5%); and
  • it was unknown why the abuse ceased (17.5%).

Intellectual and physical disability

Children with a physical disability are more vulnerable to abuse than able-bodied children (Higgins, 2010). Sexual abuse may also occur if one child is not aware (or does not have the ability to be aware) that another child is receiving sexual gratification from an interaction (Pratt et al., 2010).


Although there are studies that define sibling sexual abuse as possibly occurring between brother and sister, sister and sister, or brother and brother, the most common type of sibling sexual abuse occurs between a brother and a sister, with the brother as the abusing sibling (Carlson et al., 2006; Welfare, 2008). This is followed by brother and brother sexual abuse (Krienert & Walsh, 2011).

Most studies do not explore same-sex sibling sexual abuse in any great detail (Krienert & Walsh, 2011). Research into child sexual abuse and adult sexual assault attest to there being specific cultural and gendered barriers for male victim/survivors to disclosing abuse of any kind (Foster, 2011).


3 Sibling connotes biological, half and adopted siblings.