We had a similar situation with my grandfather-in-law's daddy. But he really WAS a horrid guy. My g-i-l's mother died giving birth to him, and his daddy blamed HIM for her death (like he could help it). Abused him and threw him out of the house at age 11 - he walked all the way to some cousins who took him in. He fortunately didn't turn to a life of crime, but became a Methodist minister instead. He told my husband that it took him many, many years to forgive his dad -
We were still able to get the info, though it took us awhile.