Cousin - In - Law
If she is your sisters daughter then she is your neice :)
She is your niece.
She is your niece.
Niece.
Neice
niece
your Neice
Your niece
Your sister's daughter is your niece, her granddaughter is your "great niece"... or you could just call her by name.
Your 2nd cousin
There is no specific word for the husband of your wife's sister. If you need a phrase, call him your "sister-in-law's husband."
would it be a brother in law? not sure about this one! Is it your husband/wifes daughters brother?