cousin
your second cousin- in law or by her name lol
The English language does not have special terms for a relationship involving an older, or a younger, brother or sister. Your brother's son is your nephew and you are his uncle, if you are a man, or his aunt, if you are a woman.
Your sister's son will call you his uncle, if you are a man, or his aunt, if you are a woman.
Your nephew?
You call him your nephew. (pronouced nes-few)
Your sister's son is your nephew. You are his aunt or uncle.
If your sister had a son, then he is your nephew.
Your sister's daughter is your niece. If you are a woman, you are your niece's aunt; if you are a man, you are your niece's uncle. Your sister's son is your nephew.
Your sister's son' son is her grandson. Your sister's grandson is your great nephew. You are his great uncle or great aunt.
In the English language, your sister's son is your nephew, regardless of whether your sister is older or younger than you are. All children of your siblings are either your nephew (if a boy) or a your niece (if a girl).
Your father's sister's son (or daughter) is your first cousin.
He would call her his aunt.