A big sigh here from me! How can a grandfather be so mean, especially to someone vulnerable? At least it stopped, and as you say, it must have made him realize what he had done!
A dear friend of mine was one of four children, and when in her teens, her father told her Mom to choose between him or the children. It is unbelievable that a father could do that!
He moved to a city some 10-hour drive away, married someone else, and apparently, her children and grandchildren adored him!
Why he was like that to his own blood is beyond comprehension, her mother had to support them on her own!
He started writing letters to her oldest son, and when he got cancer, she and her siblings drove all that way to see him.
She never forgave him, and I don't blame her!
"Street angel, home devil"
Very apt!
Interestingly, several of the commenters on my post, and others about fathers, say their father was affable outside the home, and cruel inside the home. My husband was one of them too (I married my father). It's very common apparently! I'd say "like father like son" but my husband's father was a sweetheart through and through. I lived with them for a few months, knew him for several decades, and never saw an unkind thing from him.