Son Gohan is also
Son Goku's adoptive father
in
Akira Toriyama's comic series
DragonBall.
(Due to
Chinese naming conventions, Sr. and Jr. are not added to the names of
Goku's father and
Goku's son in the story. In this writeup, I mainly talk about Goku's father.)
During his youth, Gohan learns martial arts under
Mutaito, along with his peer
Mutenroshi (Master Roshi) and others. Both Mutaito and Mutenroshi die on different occasions upon performing a suicidal move called the Mafuba against
Piccolo. The Mafuba involves trapping a person or a demon into an electronic rice cooker labelled with a written spell.
After becoming an
elderly, Gohan discovers
Goku who fell from the heavens in a space capsule, and decides to adopt him. At first, Goku is a violent
Saiyan from
planet Vegeta intent on the destruction of the human race, but becomes a "normal" child after Gohan tosses him off a cliff and gives him
amnesia. Growing up in an isolated mountain, Goku learns manners and some martial arts from Gohan.
Later, Gohan is killed by none other than
Son Goku
himself during one of Goku's full moon
shapeshifting berserker rages. Goku doesn't remember his berserker rages, but later puts 1 and 1 together to figure out what really happened. After Gohan's death, Goku believes that Gohan's spirit resides in the four star dragon ball. The same four star dragon ball appears as a decoration on Goku's son Gohan's childhood hat.