Your daughter's husband is your son-in-law. His brother is not related to you. If you need to refer to him other than by name you can say "my daughter's brother-in-law," or "my son-in-law's brother."
Your sister-in-law's daughter-in-law is not related to you but the daughter-in-law's daughter is your great niece. You are her great aunt (if you are a woman) or her great uncle (if you are a man).
The possessive form of daughter-in-law is daughter-in-law's.Example: My daughter-in-law's name is Margaret.
The word "daughter" is a noun.
Daughter in law is the name given to your son's wife
what is the plural form of daughter in law?
ex-daughter-in-law
Your daughter's sister-in-law is either the sister of your daughter's husband or the wife of one of her brothers. If your daughter's sister-in-law is the wife of one of her brothers, then you would refer to her as your daughter-in-law since she is married to one of your sons. On the other hand the English language has no special term for the relationship between you and the sister of your daughter's husband. If you need something, you will have to call her your "daughter's sister-in-law" or your "son-in-law's sister." Perhaps your daughter has a half-brother who isn't your son, but whose wife is still your daughter's sister-in-law. In that case, this woman is not directly related to you. Not everyone likes to make such distinctions, and perhaps you could consider her to be an honorary daughter-in-law of yours, in the interests of friendship.
Spanish for daughter-in-law: nuera
Your daughter-in-law's sister is not related to you, but is your son's sister-in-law.
To make "daughter-in-law" possessive, you simply add an apostrophe and "s" at the end of the word: daughter-in-law's. For example, "My daughter-in-law's car is parked in the driveway."
If your daughter's brother-in-law is the brother of your son-in-law he is not otherwise related to you.If your daughter's brother-in-law is husband of her sister, then he is your son-in-law.