I don't think you're being selfish. And as a parent I cant ever see having one of my kids pay my mortgage for me like that. Especially if they own other property! You are supposed to raise kids to be independent and successful in their own lives, not pay for yours! I would be so livid.

Have you explained your feelings and why to your husband? Has anybody talked to his parents about what a burden they've placed on you guys for all these years?