Though my situation is different in that he wasn't diagnosed with Downs Syndrome, I was sexually abused by my male cousin too-- it's really hard to talk about it but it's even gotten easier in the last day at least. Hopefully someone will be able to help you here too. I've been typing with replying to this myself but I figure maybe it's good to talk about a cousin/cousin situation eve if I can't match the DS discussion.

You can talk to me if you want