Where do you draw the line with and ex?

My fiancé and I have been together for 3.5 years. He has two kids from his first marriage (12&16). He is currently paying child support and alimony in a total of about 3k per month. When he goes to see his kids they have worn out shoe and cloths. His ex is always saying she has no money; their electricity and water are always being turned off because she is not paying the bills. Her car has been impounded and he takes her to get groceries and pays for them. I just don't get it. She is a smart woman who is capable of working but chooses not to. The kids are on his insurance, but she is constantly asking him for money and bailouts, and then says she can't count on him for anything?!? Where is all the money going? This is driving me crazy be cause he is spending so much time taking care of her issues that our plans of moving in and getting married are on hold. I know he has an obligation to his children to insure their well being, but it's turning into taking care of her too, which I feel is not his/our responsibility. So where do you draw the line? Any advice?

qkat welcome to the forum

Isn't there something he can do that have one or another official institution he can approach (perhaps via court)that can watch over where his money to her go to?