Kakarot and Raditz comes from a alternate timeline where Goku is found by the crane school instead of grampa Gohan(he don't know the main the timeline) he grows up with his memories and grows up in the crane school and train with tien and the other students. There is no Goku in this timeline, this is kakarot. Later he's found by Vegeta and nappa and works for the Frieza army before betraying all of them and join with turles,him and turles got stronger with the tree of might and killed Frieza.