When I was younger (9), someone four years older than me (13) touched my breast and genital area while I was sleeping. Would this generally be considered child-on-child sexual abuse, or would it be viewed as criminal activity in most places in the US?

This situation would generally be understood as child-on-child sexual abuse (COCSA). The four-year age gap, the nature of the touching, and the fact that one child was asleep are all significant factors that indicate this was an abusive situation rather than age-appropriate exploration.

Whether this would be considered criminal activity varies by state. Many jurisdictions have laws addressing inappropriate sexual contact between minors, though the legal system often handles cases involving younger individuals differently than cases involving adults. Some states might classify this as a criminal act, while others might address it through family court or child welfare systems. The legal response depends on the specific laws where this occurred and the particular circumstances of the situation.

It's important to recognize that sexual curiosity is a normal part of development, and at 13, someone is still learning and growing. However, this doesn't make the behavior okay. Touching someone sexually while they're asleep crosses important boundaries, regardless of the age of the person who did it. Understanding that harmful behavior happened is separate from understanding that young people can learn, change, and move forward in healthy ways.