Why are you guys even offering to pay for everything? If you can't afford it then maybe you should stand up and tell him off. He's using/making you spend money because he knows he can- why? Because you're the ones letting him walk all over you.
There's no way he will stop or change, and honestly I don't blame him because it's your family who has to shut him off. There's a limit to catering to your family's needs but when you yourself don't have the funds or time, tell them to do it on their own.
This.