“...an incident..” EUphemism is always so pleasant
You know I loved my father deeply. When he passed I sang him home. But the truth is ( and I said so at the time) and was that he was a ridiculous alcoholic who betrayed his family and his profession. When his second wife suggested I was being to hard on the newly departed I simply asked her if she prefered it if I told her what I thought of her as a home wrecker?
My father's brother sounds like the same as your Dad. He deeply wounded his kids when he left home with a younger woman and ended up leaving everything to the child he had with his second wife. He died of alcohol-related causes.
My own father insisted to his nieces and nephews that his brother was a "good man at heart." Told my Dad to cease and desist but he didn't get the deep pain he was causing.