Gohan- The son of Goku and one of the strongest Saiya-jins in Dragon ball he was trained by piccolo during the Saiya-jin saga and during this he learns of how great his power is. In the Cell Series he becomes a Super Saiya-jin and he also becomes the first Super Saiya-jin to go to the next level SSJ2(Super Saiya-jin 2).
Goku- He is the main focus of the Dragon ball series he is one of the last remaining
Saiya-jins and is the one who defeated Freeza after becoming the first Super Saiya-jin in many years.
Goten- He is the second son of Goku and Chi Chi unlike Gohan he doesn't study but is the youngest Saiya-jin to go Super he is trained by his mother and Gohan.