If he is your brother in law then his sister is your sister in law. So your sister in law's daughter would be your niece.
Your sisters daughter is your niece
Sister in law
Your neice by marriage
Your sister's daughter would be considered your niece.
The relationship to you would be your cousin !
Your sister's daughter is your niece and you are her aunt (if you are a woman) or her uncle (if you are a man).
No. This is a religious relationship, not a family relationship.
First cousins once removed.
Your aunt is the sister of either your mother or your father. Your aunt's sister is either:your mother, and her daughter is you (if you are a girl) or one of your sisters, oranother one of your mother's sisters, and her daughter is your first cousin, or,one of your father's sisters and her daughter is your first cousin.
You are an uncle or aunt, depending on your sex. If 'y' meant you - I've no relationship with her at all
Your younger brother's wife's sister's daughter would be your son's cousin.
Your daughter's step-sister would be your step-daughter.
Your aunt's daughter is your first cousin.