Most sexual abuse offenders are acquainted with their victims

In North America, for example, approximately 15% to 25% of women and 5% to 15% of men were sexually abused when they were children. Most sexual abuse offenders are acquainted with their victims; approximately 30% are relatives of the child, most often brothers, fathers, uncles or cousins; around 60% are other acquaintances such as 'friends' of the family, babysitters, or neighbors; strangers are the offenders in approximately 10% of child sexual abuse cases.

Source:http://en.wikipedia.org/wiki/Child_sexual_abuse