Your sister's sister is your sister.
Your sisters daygter is your neice!
Your sister would be her great aunt and she would be your sisters great niece.
Your sister and your wife are sisters-in-law to each other.
Your father's sister is your aunt and her son is your first cousin.
Your sister's son is your nephew His sons are your grandnephews, and his daughters are your grandnieces.
Your sister's son is your nephew His sons are your grandnephews, and his daughters are your grandnieces.
Miss Watson is the sister of Widow Douglas.
The relation of the mother;s sister to daughter is niece-aunts.
Your daughter and your sister's child are first cousins. Your daughter and your sister's grandchild are first cousins, once removed.
Your sister is great aunt to your daughter's child. The child is your sisters great nephew (if a boy) or great niece (if a girl).
If your niece's is by your sister but the brother is by your sisters new husband & another woman there would be no blood relation. If not then he's the nephew
Real sister, half sister, or step sister