句1：For anyone of Scottish ancestry, the kilt is a symbol of honor for the clan which they belong.

句2：The various plaids that one can see are the colors of the paticular clan that the wearer belongs to.

句1中的belong没有to，句2中的belong有to。

这两个句子应该都是既可以用which也可以用that的，那么belong的用法也应该统一。是否应该把句1中的which they belong改为they belong to呢？