Both my grandfathers were alcoholics. Evidently, my paternal grandfather was not a very nice man in general, and when he drank...
My mother's father, well, he could be downright abusive. Then, when my brother was a baby, grandpa had a stroke. For the rest of his life he lived in the nursing home (let's see that's from 1981 to 2004). The change was almost overnight... quit smoking, quit drinking. His behavior was reverted to pre-WWII.
That's terrible. Being deprived of decent grandparents is just wrong, I know. And of course your parents had to grow up like that... I'm lucky that my parents turned out sane and, more importantly, decided not to make the same mistakes their parents did.