What can I do about my rude, annoying brother?

I think the best idea would be to tell him to his face how disrespectful he is. Or better, you could get a friend or yourself to show him your question....making sure he doesn't see this answer of course, and see his reaction. And then break the news that it is talking about him. Good luck. And by the way, I think your mother is irresponsible and should step up the role as a mother. Good luck!