If you're wondering if your brother is possibly being sexual then there's a huge possibility he is otherwise you wouldn't even be questioning it.

You really need to do something about this now before it escalates.I would hate for you to come back here and post an update that he has raped you or something.It does and can happen.

I am in no way saying it would be your fault or you would be responsible if it escalates to that level,just saying don't wait around taking a chance just because his place is more comfortable than a shelter.