If the brother-in-law's daughter is also your sister's daughter, she would be a niece. Otherwise, there is no relationship.
If it is your brother's child, she would be your "niece." If the daughter is not fathered by your brother, then she is your "sister in law's daughter"
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.
Your sister-in-law's husband may be your brother. If so then the brother-in-law is either your husband, in which case the daughter is your daughter; or the brother-in-law is your brother, so the daughter is your niece or the brother-in-law is the brother of another sibling's spouse, in which case the daughter is still your niece If your sister-in-law's husband is not your brother, then he is not related to you and his brother-in-law's daughter is not related to you.
Your brother-in-law's daughter is your niece.
The brother of a daughter in law is the son in law.
No, your son-in-law is married to your daughter and his brother is not your son-in-law, but simply your son-in-law's brother or your daughter's brother-in-law.
I guess you will be her uncle. Consider this case.. You have a brother and he has a daughter.. Your daughter will be a sister in law to your brother's daughter.
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 brother or sister's daughter is called 'your niece.'
He would be your brother-in-law. To your children, he would be their Uncle.
daughter's brother-in-law...? :S
Your son-in-law's brother is your daughter's brother-in-law but is not related to you.