DBZ:C Prelude

In this timeline set way in the future Vegeta had dream come and defeated goku and killed him, and at the same he felt he beep upgraded from being prince vegeta to king vegeta and as his first act as "king" he had ordered the remaining saiyans go into hiding.Vegeta knew that humans and saiyans should never be, because when they reproduce the saiyan bloods becomes diluted and the saiyan never reach thier full potential. So his next act was for the remaing two families to marry one another thus streanthening their bloodline.