(((((((Twinmommy))))))))!! I'm sorry about my goof up. I guesss i'm so used to that business with in-laws I never thought that your sister would allow her husband to act that way to her little sis. Twinmommy, sometimes we learn roles from the time we are very young about how we are supposed to function in the family. Families are often very hierarchical: often I've noticed it is the women who hold and perpetuate these hierarchies. In my family my mother plays the same games your sisters do, thank God two of my siblings and their spouses refuse to play the game, so the setup doesn't quite work for her.
It sounds like you have become the identified patient in the family. The other family members bolster their selfesteem and ignore their problems by focussing on you as the "sick one".
Once again, Dear: YOU ARE NOT STUPID OR INCAPABLE!!!!! Your siblings and their husbands need you to feel you are so they can keep ignoring their own faults. I know it is not easy for you to tell them to back off, but it sounds like either you have to start doing so, or move. It may have to start out with something small, and realize that they will be p#¤%&/ at you. Think of it as building muscle. At first it hurts, but then the muscles get strong enough to handle it without trouble. I will be thinking of you, Twinmommy. Take a pocket of hugs and use when needed