Sorry for getting back to your thread a bit late. I'm not sure I can be of much help as I don't know the details of your family dynamics yet, but I just wanted to mention that sometimes, abusers hold very idealized images of their own abusers/abuse, and will go great lengths to maintain them. I would take what's been said about your mother's relationship with her father with a pinch of salt. I wish you luck in finding more information.
"Only the solitary seek the truth, and they break with all those who don't love it sufficiently." - Boris Pasternak, Doctor Zhivago