I can't forgive my father after he cheated on my mom
Is there a reason why you can't forgive your father?
Because he caused my mom to suffer through cancer
You shouldn't hold grudges against someone over something that that happened in the past. Have you thought about talking to him about it?
He cheated on her. I blame him for everything.
I understand your anger. I would be angry at my dad too if he cheated on my mom but you have to understand that they are adults and their relationship is their business.