If someone calls me brother-in-law , what are they to me? A girl called me brother-in-law , what is she to me? A girl who calls me brother-in-law , what should I call her?
2 Answers
If the terms are being used correctly according to modern usage:
Somebody who calls you bro in law is either: married to your sister or brother, or a sister or brother of somebody who is married to you.
And if a woman calls you bro-in-law, you call her sister-in-law.
The following example should make this clear to you.
Imagine that a married couple is (according to the law) a single person.
So, according to the law. You and your wife are the same. So, her sister is for you a sister-in-law. And you are for her a brother-in-law.