My mom cut off contact with her dad a few years ago. He was always kind to me and my sister, but was always manipulative towards my mom. Then his wife died, and all that was left after grief was bitterness, so he became even more of a manipulative jerk to my mom.
It still took her two years of exhausted headaches / migraines after each visit before she could cut him off. Family is hard to let go of. Personally I wanted her to cut ties way earlier - you might owe some family a helping hand, but you don't owe them your life or your kids.