I don't like to get into family matters because I don't have the true story of what happened that made the family to fall apart. There's always two sides to the story and then the truth of what happened hence unless the truth is opened to the public, I don't like to get involved but what I want to say is that, when the parents treat their children rights, the children won't turn their back against them. It's always the situation of the parents being bad first to the children that makes the children turn their back against them in their old age.
You have a good point, but don't forget his wife can play like a victim by acting like his dad is a bad person or she threaten his son to not looking back/help his father, otherwise all benefit given by his wife would be stopped. Let's say, you as a son, will you choose to become poor just because you want to stay with your father? assuming you know your father is really a good man, however your mother also a good person too.
Your mother looks bad on your father's story, not on your story.