Is there a term for the sibling of ones son-in-law or daughter-in-law? Real-life example: The composer Dohnanyi had a son who married a sister of Dietrich Bonhoeffer. So Dohnanyi was the father of Bonhoeffer's brother-in-law, or the father-in-law of Bonhoeffer's sister.

Is there an accepted term for this relationship?


With respect to Dohnanyi, Dietrich Bonhoeffer could be referred to as:

  1. His son's wife's brother (for most detail),
  2. His son's brother-in-law, or
  3. His daughter-in-law's brother.

Relatives through marriage are generally known as "affines" or "in-laws", and only the close relationships have a specific term.

This is only for English. There may be one or more other languages that have a term for this relationship.

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Steve Morse's relationship calculator shows that there is no blood relationship and no English term.

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