Goten's father is Gokou, and has an older brother named
Goten. We don't see much of Son Goten during the
DragonBall and DragonBall Z sequel. Apparently when Goten
and Chibi Trunks first appeared, it was already near the start
of the Majin Era. Goten has supernatural power just like the
rest of the Saiyan, however, Goten is an exception. Goten
reached to the Super Saiyan level without pushing himself to
the limit like what Gohan and Gokou had to go through.
When Gohan was training with Goten, Gohan asked Goten if
it's possible for him to become a Super Saiyan. Goten just
gave it a try, and without trouble, he transformed into a
Super Saiyan.