Should we interfere?

My daughter has her own house where she lives with her partner of 5 years and their 2 young children. He is a self-employed professional man who SEEMS to work all the hours possible but has no money. He owes thousands to her and to us. She supports all of them with extra help from us. He is a pleasant, friendly man, wonderful with the children. We pay for holidays, flights etc., which he cheerfully accepts. She constantly moans to us about her situation with him and we sympathise but don't interfere. She loves to work but expects him to do his bit too. When can we say to him that enough is enough? It is none of our business but she involves us. This situation surely can't continue indefinitely. It's very mysterious. Does he have huge debts to pay off, is he supporting his parents? Who knows. We can't leave her to starve or lose her house because of non-payment of mortgage but this situation surely can't continue - we'll be broke. Advice and solutions please.