Son Gohan, also known as Grandpa Gohan, was the man who found Goku when he was sent from planet Vegeta(Saiyan's planet) to Earth to destroy all life forms on it. Son Gohan raised Goku, even though Goku was a mean and angry child. One day the two were walking near a ravine and Goku fell into it, hitting his head. He should have died from the fall, but lived with only getting a concussion. The next day Goku awoke being a gentle-hearted and kind kid, forgetting his mission was to kill everything on Earth. Son Gohan passed away in Dragon Ball when Goku looked at the full moon. When a Saiyan with a tail looks at the moon, they become a gigantic ape that will destroy anything in its way. This happened to Goku and he accidently killed Grandpa Gohan. Goku didn't find out until he was older that this happened to him. Son Gohan trained along side the Ox King with the invincible Master Roshi.
Ox King
The Ox King is the father of Chi-Chi, which is Goku's wife. He was said to be a cruel and mean king of Fire Mountain, but turns out he was actually very nice and wouldn't hurt a fly. He is really large and has a lot of facial hair.