Ipar doesn't require a gender in translation, so "Who is your in-law?" could also work.
I think in-law is generally for your spouse's parents, not siblings.
why isn't sister in law also acceptable???? the statement was not gender specific....
Yes, but I don't recall that they gave sister within the list of possible words to select from, so I do believe the answer in this case is specific.
In-law can be sister or brother. This is BS answer
Good one - 'sibling in law' makes more sense