I want to know what name is given to the relationship of a person to his/her brother's wife.
Unlike other languages, English has only one one term for:
My brother's wife.
My husband's sister.
My husband's brother's wife.
All are my sister-in-law.
(If you are male, then change "husband" to "wife," obviously.)
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.