I'm rely worried about my brother?

If he said he had nothing to live for, that means his suicidal and you can't just wait to let him come out anout it. Unless you speak the language of dead people. You need to let him know. But bring it up slowly. Start a convo that might lead to that. Or say "dude, help me please, my friend wants to kill himself cause his gay. But I don't understand because I'm here for him and like him the way he is!" Then maybe he will know its more like a brother than a friend;)