Here's a response from a male survivor:
1) The fact that he told you means that he trusts you immensely. Good for you.

2) Thanks for believing him.

3) It would be great if he could get help, including from this site. You might tell him it is here, but tell him you don't need to know his name if he comes here. For some people this place works best when they know that nobody they know can link their posts to them.

4) You can get help, too. You might need some support in learning how to set your boundaries in a way that respects his struggle.

5) In my opinion you should under no circumstances talk to his sister or anyone else in his family about this. He told you in confidence. Don't break it. You might get advice from professionals about how to protect kids at her school adn in her family.

You must be a great support to him. I'm sorry if you get anger that might be better directed at someone else. I hope he learns to handle that better.
"This is not my shame, this is their shame." Mona Eltahawy