It's really hard to say what could be causing his behavior, because it could be anything of those reasons you listed or it could be a combination of several of them. Is this behavior unusual for him, or has he seemed to have these tendencies pretty much ongoing? I think that would factor a lot in trying to figure out what is going on with him. If it's been ongoing all his life, then it sounds like he has some behavioral problems that perhaps medication could help with. If it seems like it has come about in him as a change, then I would think it's a response to his envionment and what's going on in his life, in which case he probably needs some counseling. Good luck to him and your family, I hope things work out well for him.