Twin souls are not exactly the same as soul mate.

双生灵魂与灵魂伴侣不完全一样。

youdao

A related concept is that of the twin flame or twin soul - which is thought to be the ultimate soulmate, the one and only other half of ones soul, for which all souls are driven to find and join.

一个相关的概念是，双火焰或者双灵魂。一个人只有一半的灵魂，而所有的灵魂就是要找到另外一个灵魂并且二合为一。

youdao