Goku Jr.

Goku Jr. is a descendant of Goku, he lives 100 years after the defeat of Omega Shenron and is destined to be the next protector of earth together with Vegeta Jr. 

However, Goku Jr. feels weaker than all other Saiyans of Earth and wants to be trained, he also wanted to meet the other Saiyans so he decided to go search for the Dragonballs 

In episode 20 of Dragonball After (Ultimate) Goku finally gathered the seven Dragonballs and wished Shenron to make all friends of 100 years ago revive, this wish was granted but because of the high amount of power Shenron needed, a Dark version of Shenron in another universe was able to to revive a villain with a power level of 5,000,000,000. the dark dragon decided to revive Kid Buu, with this amb azing amount of ki.

All of Goku's friends were revived, when Goku found out, he decided to come back and train Goku Jr. to make him the next protector of Earth, also Bulla and Pan were granted eternal youth (this was a 'little present' of Shenron for having defeated Omega for the second time)

Goku also has the ability to transform into a Semi Super Saiyan