Your sister's husband is your brother-in-law.
The daughter of his sister is his niece, and your sister's niece, but is not related to you.
Assuming the child was born to the woman before she met your brother, the daughter of the woman whose brother married your sister is not related to you.
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.
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.
Being your sister's brother or sister you would be an uncle or an aunt to her 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 fiance's sister is not related to your brother or sister. However, once you are married and your fiance is your wife, she will be their sister-in-law and they will be her brother-in-law and sister-in-law.
When your sister-in-law is the sister of your spouse, her sister is also your sister-in-law, unless she is your wife.When your sister-in-law is the wife of your brother, her sister is not related to you.
If your sister-in-law is still married to your brother and her daughter is the biological child of your brother you would be the child's great aunt or great uncle. If your sister-in-law is the sister of your husband, her daughter's baby is your great niece or great nephew, and you are the baby's great aunt or great uncle.
Abraham married his half sister Sarah. Gen:20:12: And yet indeed she is my sister; she is the daughter of my father, but not the daughter of my mother; and she became my wife.
Your brother's sister is your daughter's aunt, and your daughter is your brother's, and his sister's, niece.
There are three possibilities:If you are male, your sister's sister-in-law could be your wife. Then the sister-in-laws's daughter is yourdaughter.Your sister's sister-in-law could be the wife of your brother. Then the sister-in-law is your sister-in-law, too, and her daughter is also your brother's daughter and thus your niece.Your sister's sister-in-law could be the sister of your sister's husband. Then the sister-in-law is not related to you, and neither is her daughter.
Your brother or sister's daughter is called 'your niece.'
Your sister's daughter and your sister's brother are niece and uncle to each other. The daughter is the niece of the brother and the brother is uncle to the daughter.