Having a conversation this weekend, and this came up. Naively, I'd be inclined to simply label the brother of my brother-in-law a brother-in-law as well, since we've joined the families in a sense.

Specifically, my wife's sister's husband has two sisters. I call him my b.i.l., would they be s.i.l. by extension? Is this acceptable usage, or must I trod laboriously through the above description every time I describe the relationship?

  • What language do you speak natively?
    – NVZ
    Feb 20, 2016 at 13:56
  • 4
    Related question, Name for the relationship of wife’s sister’s husband.
    – user140086
    Feb 20, 2016 at 14:02
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    It depends on the family and its customary usage. (In ours, it's "that idiot.") Otherwise, generic "brother in law" seems to be sufficient to get into the bratwurst queue at the family picnic.
    – Rob_Ster
    Feb 20, 2016 at 16:18
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    Because we had kids, we referred to my wife's sister's husband's sister as "Aunt Cindy" for convenience.
    – Jim
    Feb 20, 2016 at 20:49
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    Related: genealogy.stackexchange.com/questions/6818/…
    – Chenmunka
    Mar 15, 2016 at 10:38

1 Answer 1


One rarely used word for this is co-brother-in-law

  • An uncommon secondary usage of this term... but I suppose it'll have to do unless we get a better answer.
    – Jeff H.
    Mar 10, 2016 at 0:20

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