What should I do if my sister marries my brother?

What about my sister's married brother?

Take good care of your sister. A younger brother should first wish his sister and brother-in-law love and respect each other. And give the groom a certain reminder at an appropriate time.

What an elder sister needs to do when she marries a younger brother is to take good care of her elder sister and give the groom a certain reminder at an appropriate time. There is also the need to help my sister put on wedding shoes, accompany her, ride in the same car as my sister, and finally have a younger brother to help her present flowers at the wedding.