An example:
I have a wife. My wife has a sister. And she (the sister) is married.
Question:
What is the relationship between me and my wife's sister's husband? Is it brother-in-law?
Yes (at least that is what I call my wife's sister's husband).
John
I have jokingly called mine my "brother-in-law-in-law" because it's through two marriages that we are related. But in real situations, like JohnP, I just say "My brother-in-law."
If it's important that people understand the relationship, you can say "My wife's brother-in-law." That can only come to pass if your wife has a married sister. Your wife's other brothers-in-law can be your own brothers, but you wouldn't refer to them as "you wife's brothers-in-law." You'd just say "my brothers," unless you were trying to be cute.
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.
"Brother-in-law" normally refers to two different relationships:
Your wife's brothers
Your sisters' husbands
It's not a huge stretch to use it for your wife's sisters' husbands. There really isn't a better word for such a thing.
I don't have a problem with just calling him my brother-in-law.
We're spending Thanksgiving with my sister-in-law and that guy she married... probably not very gracious.
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.