I see that no one seems to explain how someone becomes uncle dad, so I will take the stage. Someone becomes your uncle dad when your dad has sex with his sister (your aunt), producing you in the process. It is that simple. You don't even know if you should call him dad or uncle, so you call him UNCLE DAD.
It was a fine day in Lincoln Park. Joe saw his sister, Meg, was wearing provocative clothing. Before he could control himself, he felt Johnny Wank get excited and start to yell for more. There was only one way to get Johnny Wank to shut the fuck up: bang his sister. His sister was unlikely to comply with this incestuous deed, so he creeped up behind her and smacked her ass real hard. That took her by surprise and then he ripped off her clothes and raped her before she could do anything to stop him. When he was finished he ran away. Later, when Meg gave birth to a boy named Dale, Joe returned. Dale learned to call his male parent Uncle Dad and his female parent Aunt Mom. Life just sucks sometimes.