相あい婿むこ

noun

brother-in-law (husband of one's spouse's sister)

Refers specifically to the husband of one's spouse's sister. This is a reciprocal relationship: two men married to sisters are 相婿 to each other.

• 彼かれは私わたしの相あい婿むこで、妻つまの妹いもうとの夫おっとです。

  He is my brother-in-law, the husband of my wife's younger sister.

• 相あい婿むこ同どう士しで飲のみに行いった。

  The two brothers-in-law (married to sisters) went out for drinks together.