What Do We Know?

The best estimate based on current research is that only about 12% of those who are affected by sibling sexual trauma ever tell anyone about it [1]. But, it is impossible to truly measure how many never tell, even anonymously to a researcher.

With that in mind, 5WAVES estimates that at least 5% of children are affected by sibling sexual trauma [2]. This means that it is approximately as common as childhood food allergies [3].

Leading researchers suspect that sibling sexual trauma is one of the most prevalent forms of child sexual abuse [4].

Sibling sexual harm starts earlier, lasts longer, and is more frequent and severe than other child sexual abuse. In half of all cases, the harm to a child begins before their 8th birthday, and lasts more than 5 years [5].
The consequences of sibling incest are as serious for the survivor as adult-child incest. They include anxiety, depression, shame, Complex PTSD, difficulty maintaining stable and trusting relationships, stress-related pain and physical illness, increased risk for substance addiction, eating disorders, self-harm, suicide, sexual exploitation and victimization into adulthood [6].
Children who bear the responsibility for sexually harming a sibling, or who felt at the time that they were a willing participant, are still likely to suffer lifelong negative consequences including shame, depression, anxiety, low self-esteem, and increased risk for suicide and addiction [7].
Adults, including parents and professionals, find it difficult to accurately assess and appropriately respond when they learn of sexual behavior in children. In a survey of professionals who respond to reports of child sexual abuse in the UK, 73% reported they had received inadequate training about sibling sexual behavior, with many reporting no education or training whatsoever [8].

More than ⅓ of sexual harm to children is caused by other children or teens [9].
Sexually abusive behavior toward young children appears to peak at age 13-14 [10].
Although the harm to their siblings is serious and real, and the short-term risk for relapse is high, factors that lead children and teens to make this tragic choice are very different than for adults who sexually abuse children [11].
Several studies based on cases entered into the criminal legal system have found that less than 10% of adolescents who are charged with a sexual offense of any kind will be arrested for another sexual offense as an adult [12]. Although most instances of sexual harm are never recognized by the legal system, and there are no studies specific to sibling sexual abuse, these studies suggest that a large percentage of juveniles who engage in harmful sexual behavior do not continue to do so as an adult.

Cautions on the use of these studies:

General estimates of reoffense rates cannot predict whether any individual person will cause harm again. Every situation is unique, and adults must make victims' and children's safety and healing top priority.
Research is needed that looks at risks specifically for those who have sexually harmed a sibling, and that include data from other sources in addition to the criminal legal system.