I have been watching a lot of KOTH on Cartoon Network, and I discovered something awesomely funny. Hank's Dad, Cotton was an Adult Baby.
His wife, Didi was a nurse, and she would coo him, and take care of him like a baby. He routinely sat in high chairs and booster seats. If you watch episodes with him, there are lots of hints.
It also explains his macho attitude, and why he was always bragging about killing fiddy men. Because he was keeping a front.
They never mentioned if he wore diapers, nor if Didi changed him.