What would you do when you ask a sibling for help but you never get it?

I wouldn't cut ties with either of my 2 brothers over what you describe, but I would have zero expectation of any help from them either. In return I'd be unavailable offer him rides, as giving/getting favors is a two way street. He may be one of those people who resents being on a timetable and wants to do things on his own - a "play it by ear" type of schedule, which could be difficult for you if you want things to get done.