My brother is suicidal, what should I do?

I'm no expert but i suggest you go with him and take up some sort of hobby together to keep him away from the drugs and untoward thoughts. When ppl are depressed a lot of the time they dont know how to help themselves or else think about it but dnt have the courage to actively work to better their situations. Your situation sound pretty messed up but not completely hopeless i hope it gets better. Sorry i couldn't be much help.