For what it is worth, I've known many people who were molested as kids who wouldn't EVER do that to another child. A lot of sexual abuse survivors do not admit what has happened to them because they are afraid of the kind of judgment that has been displayed here tonight on this board. Now, I'm not saying he is NOT a paedophile and I would question him very closely about his CURRENT state of mind in regard to his sexual attitude towards children and watch him closely when it comes to how he behaves around children now. That's what is important here. Also, has he ever received any counseling to deal with what happened to him, and his own perpetration of abuse as a young teenager? You have to understand that, at 13, after 4 years of abuse, this was an immature person, with delayed emotional development, with a lot of serious sexual issues surrounding power, control, shame, guilt, anger, etc. who acted out his own stuff with other younger children, as had been done to him. No, it wasn't right, at all, on any level, but neither was what happened to him. A cycle of abuse perpetuated, because no one protected him, nor helped him, nor listened, nor paid attention to the changes in behaviour he was displaying as a result of what he went through.
It is a documented FACT that boys who are abused are more likely to become paedophiles themselves if they are not counseled. Ultimately, you have got an upfront warning about him and it is up to you whether you can live with the knowledge that he may still have these tendencies within him if he has not come to terms with what happened and what he did. It is possible to have gone through what he went through and to come out the other side as an adult who is is only attracted to adults. If he has trusted you enough to admit these things, I would say that there is a greater possibility that he has healed to a degree from his earlier experiences (it is a lifelong journey and some stuff will be permanent, but not necessarily making a him a paedophile). Most paedophiles are extremely cagey and very wary of admitting anything that will mark them out as "different", however, their actions will show them up eventually. They are "odd" around children - i.e. raking kids over with their eyes when they think no one is looking, etc., paying them attention over and above adults in a room, or putting themselves in positions where they can meet them, obviously approaching them and talking to them "first", or knowing a lot about kids interests, as well as displaying controlling tendencies, stuff like that. They have a warped belief that kids are seductive and want sex with adults, but they are normally clever enough to realise that they have to be covert because the majority of society despises this kind of behaviour. However, they do slip up, even when trying to behave "normally". If he is a paedophile, there is no known cure. Unless he has a highly developed conscience, he will want to act on the urges. Whatever the truth of the matter, I wish you all the best.