For example:

  • I have a sister named Charlotte
  • Martin has a brother named William
  • Charlotte is married to Martin

Martin is my brother-in-law, but what is William to me?

I originally posted this question on English.StackExchange. A commenter referred me to ask it on this stack.

  • 1
    It was my understanding (although not verified) that the term brother/sister/father/mother-in-law was originally because the families had both recognised that - through marriage - they had become family in the eyes of the law. So I guess technically it would be brother-in-law. Although this isn't commonly used in everyday English language. – AvieRose May 28 '13 at 20:08

There is no common word (though see below) for this relationship in English, but there is one in Spanish: concuñado/a. So William is your concuñado. This word is used a lot at some of our family gatherings.

Note that cuñado/a is Spanish for brother/sister-in-law.

However the terms co-brother-in-law and co-sister-in-law are sometimes used for this in English, but they are generally used when translating to English from a language that has a specific word for the relationship.


Well there isn't a special name for this - he is just your brother-in-law's brother.

  • 5
    Or your sister's brother-in-law. Choose whichever seems more obvious. Lots of "relationships" don't have names in English (but might have in other languages). – AdrianB38 May 26 '13 at 19:54

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