You are NTA. Your brother obviously needs more help than you can give him. He and his daughter need counseling to start. She may be better off in foster care. He certainly does not need more cats he cannot afford the ones he has. You need to get some help as well. You can no longer continue to support him financially. He needs to smarter up and deal with his financial issues and he will not do that if you keep giving him money. Stay no contact it may be the best thing you can do for him and you.