Idk what to put as topic name. Why can't sisters/brothers marry into the same family? For example, there are two sisters, A and B. There are two brothers, C and D, from another family. If A marries C, then B and D can't marry anymore. Why is that? Hopefully that made sense. If you watched Qe Muag Xaiv Txij Nkawm (), it's like the situation there with the sisters and brothers.