Sibling-in-law

Spouse's sibling or sibling's spouse

A sibling-in-law is the spouse of one's sibling, the sibling of one's spouse, or the spouse of one's spouse's sibling. In Indian English the latter can be referred to as a co-sibling (specifically a co-sister, for the wife of one's sibling-in-law, or co-brother, for the husband of one's sibling-in-law). More commonly, a sibling-in-law is referred to as a brother-in-law for a male sibling-in-law and a sister-in-law for a female sibling-in-law.

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