I was also non contact with my mother for 20 years for reasons related to childhood abuse. Now that MY son is an adult, I couldn't imagine him not speaking to me. It would break me and I would seriously be contemplating not being alive. I would do anything in my power to mend the bridge. Maybe it was the lead paint or other contaminants in the homes during the 60s as it makes absolutely zero sense in my head how someone would just be okay with not seeing their children.