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.
Daughter in law is the name given to your son's wife
The possessive form for the compound noun daughter-in-law is daughter-in-law's.Example: My daughter-in-law's shop will do my hair for free.
Daughter is a noun.noun
ex-daughter-in-law
what is the plural form of daughter in law?
The plural of daughter-in-law is daughters-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.