your brother's daughter is you niece
brother's daughter relation
Your brother's daughter is your niece. Her daughter is your great niece.
Your brother's son or daughter is your nephew or niece respectively.
Your mother's brother is you uncle and your daughter's great uncle. Your daughter is his great niece.
Your grandfather's brother's daughter is your first cousin, once removed.
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.
3rd cousin I think:-)
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.
niece
If you are married to your daughter's mother, then her boy is your stepson. If you are not married, then he is no relation to you. Either way, he is your daughter's half brother.
If your brother-in-law is your spouse's brother, then his sister's daughter is your spouse's niece, and your niece, too. If your brother-in-law is your sister's husband, then his sister is not related to you, and neither is her daughter.