There's no way that grandpa was a normal person, he's probably a war veteran

It would probably be more fun if instead of a war veteran he was a target by a both sides of west and east since he created war weapons i would say this would be a oppenheimer story and he created nukes in his prime and he hated that so he went into hiding afterwards?

Okay that does seem more fun now you got me hoping he's targeted by both sides and disgusted by his own doing