Well, your not quite sure about him being homosexual. But I think he needs someone to talk to. Having his uncle die is very devastating and he needs someone to talk to, and that''s you!
Tell him that you''re there for him no matter what, and that you''re very worried about him because he''s been acting a little different lately. Take a time and sit with him to talk about this. Don''t mention anything about being homosexual though. He might tell you he is or if he''s not. Or he might not touch the subject. He might just be depressed and a little confused, so just give him some time and a friend he can rely on for everything