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.
彼は私の相婿で、妻の妹の夫です。
He is my brother-in-law, the husband of my wife's younger sister.
相婿
The two brothers-in-law (married to sisters) went out for drinks together.
義弟 is a general term for younger brother-in-law, whereas 相婿 is a reciprocal term for men married to sisters.
Standard kanji spelling for 'brother-in-law' (husband of one's spouse's sister).
Variant kanji form using 聟 (a less common character for 婿).
Compound of 相 (ai, 'mutual') and 婿 (muko, 'son-in-law' or 'husband'), literally 'mutual son-in-law', reflecting the reciprocal relationship between men who marry sisters.