Since both twin sons have adopted the word Zhou Xiaoyun, it is better for the third son, whether it is a son or a daughter, to fight, and others will know that they are family as soon as they hear it. If they are daughters, they can be called: Zhou Xiaoyi, Zhou Xiaoying and Zhou Xiaoxun.
If it is a boy, you can call:
Zhou Xiaoyu, Zhou Xiaohan, Zhou Xiaoxi, Zhou Xiaoyan
Hope to adopt