this situation exists between my real mom and her parents, and it's something my t and i have discussed lately.
my grandfather sexually abused my mother, possibly both my uncles and several cousins (by blood) as well as close family friends. my mother had a child when she was 14, who my grandparents raised as their youngest 'son'. i was also abused by my grandfather and neither my 'uncle/brother' or my other true uncle will let my grandfather around their kids without direct supervision.
appearances are everything to my grandparents, especially my grandmother who has an emasculating queen personality. they have hid many family secrets, bailed my real mother out of every financial mess she's ever gotten herself into, my grandfather got scripts for her to kick her coke habit and got her hooked on painkilllers instead, she's lived with them off and on since i can remember, they foot the bills for everything for her, yet let my uncle and 'uncle brother' struggle through every imaginable financial woe, always focusing on her- they only reason to me is because they are afraid to tell my real mom 'no' because she would out them for the abusers they are. my real mom, being the con artist she is, is working it as much as she can. her and my uncle and 'uncle brother' had equal shares of the house, etc, but i would bet dimes to dollars she's got it all in her name now.
they enable her because it's easier to go along with her and pretend it's all sunshine and roses as to my grandmother, how they appear in the community is everything and this kind of behavior would remove their status.