What to do with 13 yr old son who has repeatedly abused 4 yr old sister, sexually

The daughter told what happened, but she said it had happened only once. Child services was called and the son ended up on informal probation for the incident and underwent counseling. We have now found out that the abuse was ongoing, hasn't happened since she told, and happened at places other than the home. What should be the next step taken. It is felt that the son should not remain in the home because of the stress and behaviour between the children. They are both under constant supervision, by an adult, so it could not happen in the future. Any advice is appreciated.

[Kevin Kennedy, Ph.D.]

You should return to the therapist (and the therapy should be in the hands of a person who specializes in perpetrators of sexual abuse) with the new information. In addition, psychological testing should be conducted.