red_dragon
I can not answer your question properly as there isn�t sufficient information.
However as a dreaded social worker I can tell you this.
The information you originally provide is a bit like a piece of string and how long it is. It could mean sexual experimentation to early sexual abuse. But, without considerably more background detail you can not possibly determine, nor can anyone else.
Social services would not be involved with him as a parent on just this, there has to be considerably more reasons. What you have said wouldn�t even result in him being on social services radar. But I don�t know what the other reasons are, and it doesn�t appear you do. It will be known by him, the mother and the professionals involved. Other than that it�s confidential.
As for 1 every 3 week contact. That is truly exceptional; it would normally be 3/4 times a week to daily. Haven�t got a clue why it is so reduced but there would have to be very serious reasons not because of his behaviour when he was 13, or because he himself was abused.
Without knowing the full details all you will get is speculation, only you can decide if that helps you or not.