Your sister's daughter is your niece.
Your brother or sister's daughter is called 'your niece.'
Your father's sister's daughter is your cousin. Therefore, your father's sister's daughter's daughter would be your cousin's daughter. In genealogical terms, she would be your first cousin once removed.
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"
Your sister's daughter is your niece. You are her aunt (if you are a woman) or her uncle ( if you are a man).
Since your uncle's sister is your aunt, her daughter would be your cousin, just as your uncle's daughter would be.
Your niece.Your brother's daughter would be your niece and you'd be her uncle or aunt. Your sister's daughter would also be your niece. If your sibling had a son, he would be your nephew.
Your sister's daughter would be your niece. You would be her aunt or uncle, depending on your gender.
niece
...niece.
Being your sister's brother or sister you would be an uncle or an aunt to her daughter.
He would be your brother-in-law. To your children, he would be their Uncle.