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Where's the Line?


“Sibling sexual abuse is sexual contact between two siblings

that is experienced by the survivor as traumatic.”  Cora Haskins, 2003


Sexual activity between a child and an adult crosses a clear generational boundary. Sexual activity between siblings is more murky. A bit of sexual play or curiosity is considered normal and acceptable. So how do adults, let alone children, know when it’s gone too far?   


Sexual activity between adults has boundaries defined by mutual consent. Even those come with difficulties. Children do not have the understanding to seek or give consent. So where is the line?   


Adults who discover sexual activity between siblings often see only a small piece of the picture. Most sibling sexual trauma goes totally undetected by adults in the household. It is very difficult for adults to discern the extent and nature of sibling sexual activity, and to determine on an appropriate response. It's all too easy to underreact or overreact, and the consequences of either can be devastating.


Choosing the words to use to describe what happened is a critical step following sibling sexual activity or its discovery.  Young children often lack the words to describe sexual violation of their body space. But if it happens between older children, or as individuals look back on the experience later in life, the terms they use to describe it will frame the narrative of their own life, their family, even their identity. The labels that parents choose will give important messages to the children about what is acceptable and whether they are believed, supported, or included within the family. The labels that outside authorities choose will influence everything from the availability of therapeutic interventions, to legal consequences, to the structure of the family far into the future.     


There are so many possibilities, and so many gray areas, that even professionals cannot agree on criteria to pinpoint the line between normal curiosity and harmful sexual behavior. The chart below is based on the work of Simon Hackett, Children and Young People with Harmful Sexual Behaviours (2010).  Its general guidelines are widely cited by researchers and those responding to reports of troublesome or questionable sexual behavior between children or teens.












































  • Young, prepubescent

  • Children similar in age

  • Lighthearted, playful

  • Mutual, voluntary

  • Driven by curiosity

  • Matches development and age

  • Brief, mostly visual

  • Socially acceptable


  • Pushes the limits of social norms

  • Often a one-time event

  • Driven by impulsivity or immaturity

  • May be outside appropriate context

  • Generally consensual and reciprocal

  • May cause embarrassment


  • Outside soical norms

  • Level of harm may be unclear

  • Consent may be blurred or hard to assess

  • May involve imbalance of age, power, status

  • May include compulsive elements

  • Not usual for developmental stage


  • Harmful intent and/or outcome

  • Initiator knows the behavior is wrong

  • Includes enticement or coercion

  • Lack of consent, or inability to give full consent

  • More likely to be ongoing

  • Often a gap in age, size, status, or social development

  • Driven by power and/or sexual gratification


  • Involves force, threats, or intimidation

  • Highly intrusive

  • May include physical violence 

  • May include sadism

  • May leave evidence of physical trauma

The same event may fall into one category regarding the motivation and mindset of the initiator, while falling into another category with respect to the way the survivor perceived it and the trauma they experienced.

Even if behavior clearly falls into the category of abuse or assault, adolescents have different motivations and pathways to harmful sexual behavior than adults who might commit exactly the same acts. In particular, teens who get treatment are much less likely to offend again as adults. 

In reality, sexual behavior in young people exists on a continuum. The lines between these categories are not at all clear. Often there are elements from different categories. If there has been ongoing sexual behavior, it may have started with normal curiosity, become increasingly inappropriate, and then abusive over time. 


Adults do need to decide rather quickly how to respond when they discover sibling sexual behavior. But they should be aware that they may need to adjust their language or response as they learn more.

Next steps for parents who are concerned about their children’s sexual behavior: Helpline is a confidential, private place to share your situation and get help on how to understand what’s happening and what to do next. They are open during business hours. For 24/7 help, contact (National Sexual Abuse and Assault Hotline)

Helping a Child Manage Unsafe Sexual Behavior | Stop It Now

National Children’s Alliance: What Happens Now: Addressing Sexual Behavior Problems with Your Child

Siblings Too Podcast: Defining Sibling Sexual Abuse (20 minutes) note: it is now recognized that sibling sexual trauma can arise from even one instance of harmful sexual behavior

Important Notes

Not all children mature at the same rate, and children who have atypical intellectual or social development are at higher risk, both to engage in inappropriate behavior and to be harmed by others’ inappropriate behavior. The level of a child’s ability to comprehend situations and social cues should be taken into account when labeling and reacting to their behavior. Unfortunately, many laws are written with age-based language that does not take this into account.  

Listen Now:

The word abuse, or sexual abuse, may have a specific legal definition that will be relevant if the social service or criminal justice systems become involved. Consult a lawyer in your state. 

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