>>283536703
>Shanks: Roger's adoptive son
>Luffy: Garp's grandson
>Teach: Xebec's son
It is what it is. You can accept it or leave it be. Honestly we'd be better off thinking of One Piece as a Game of Thrones type story than some kind of Rock Lee story. Similar case for HxH/Naruto/Bleach/etc. Like it or not, heroes and prodigies don't come out of nowhere.