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.
Speaking well of the dead probably has its place -— but I don’t know where. Someone was either a good person or they weren’t I shared some wonderful stories about my dad but the other stuff was always there because it is part of who he was.
From the outside looking in, it is easy to judge and cast aspirations towards others. Perhaps your uncle was a "good man at heart" but God will be the judge of that, not you.
"Stop judging, that you may not be judged. For as you judge, so will you be judged, and the measure with which you measure will be measured out to you.
Matthew 7:1-2