There is none.
Your daughter's husband is your son-in-law.
You are legally her aunt through marriage.
They are husband and wife.
No relation...lol
Your husband's brother's wife or your husband's sister's husband have no relation to you. Your brother's or sister's wife or husband is called a sister or brother in-law. You are only related by the marriage between them and your sibling.
There must be a sort understanding between each other
Your husband's niece is your niece, too. You and your husband are her aunt and uncle. Your brother is not related to a niece of yours who is the daughter of your husband's sibling.
No. The sister is a relation, and her husband is an in-law. The husband's brother is no biological relation either. Therefore, the great granddaughter of the husband's brother is not a relation.
He is of relation as a cousin-in-law.
Your cousin-in-law.
Your children and your husband's niece are first cousins. There is a difference of one generation between them. That makes them first cousins once removed.
Your husband's grandniece is your grandniece-in-law.