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See also: brother in law


Alternative forms[edit]



brother-in-law (plural brothers-in-law or (archaic) brethren-in-law)

  1. A male relative of one's generation, separated by one degree of marriage:
    1. The brother of one's spouse.
    2. The husband of one's sibling.
  2. (uncommon) Co-brother-in-law: A male relative of one's generation, separated by two degrees of marriage:
    1. The husband of the sibling of one's spouse.
    2. The brother of the spouse of one's sibling.


  • 1597, William Shakespeare, Henry IV, Part I, act 1, sc. 3,
    We at our own charge shall ransom straight
    His brother-in-law, the foolish Mortimer;

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Related terms[edit]


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