Can a child perpetrate sexual abuse?

Yes they are quite capable of inappropriate behavior including sexual behavior. Most professionals assume that is a strong indicator that they themselves have been abused. Childish curiosity is not abuse...the definition implies a difference in power and understanding where one is taken advantage of by another. Do children bully....of course and they lie and they steal things too...some even murder. The age of criminal responsibility in the UK is 10... below that we assume wrongdoing is most likely the result of an older persons influence. In the same way we don't blame victims of crime we also have to consider ability to understand or consent when children do wrong things.