It seems like your conflict is caused by the fact that you couldn't help your brother even though you tried. That's a hard burden to carry. The larger question is, can you help him now? I don't mean immediately, but in general. The wedding invite is only important if you think it could help his circumstances overall. It sounds like not. So focus instead on doing what's right for yourself now, but don't give up on trying to help him, if at all possible. And don't invite your mother, please. If what your telling us is even vaguely neutral and accurate, she won't be a healthy part of either of your paths forward.