The best thing to do is not to allow for them to take advantage of your availability and helpfulness. It does not sound that he is self sufficient and the fact that he feels obligated to help her, will remain to go on and on in a circle. Someone has to break the pattern
Talk to him first and then if you have to, talk to her and let her know of your position in this. It is ok to help but not healthy for him to overcompensate because she's financially assisting him. She is enabling him to continue with his behavior and his sense of obligation to her leads to co-dependence.