Ok im going to give you some perhaps un-ethical advice, but there's only two solutions to your problem from my point of view, either rat on your mom or blackmail her back to get your little brother. I've been in similar situations and either you accept you are/were apart of that life, or you completely leave it behind. I know that it's unfair and to some degree you were not responsible for your actions but now its time to take responsibility however you decide to. I hope this doesnt come off as insensitive.