So one becomes the ambitious one, and one becomes the holder of the family, the laid back counter balance.

于是，一个人成为雄心勃勃的人，一个人成为家庭的主人，一个悠闲的平衡者。

That tail works as a counter balance, so they can swing their tail one way or the other while running and that helps them turn.

尾巴能起到平衡作用，在它们跑动时把尾巴摆到一侧或另一侧来帮助它们转弯。