Sibling-in-law

A sibling-in-law is the spouse of one's sibling, or the sibling of one's spouse, or the grown-up who is married to the sibling of one's spouse.

More ordinarily a sibling-in-law is intended to as a brother-in-law for a male sibling-in-law, in addition to a sister-in-law for a female one.

Sibling-in-law also talked to the reciprocal relationship between a person's spouse as living as their sibling's spouse. In Indian English this 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.

Rarer use of the term is seen in "casual conversation" with the term brother-in-law describing the relationship with one's brother-in-law's brother: William's brother Charles has a brother-in-law called James James being Charles' brother-in-law here not by virtue of marrying his sister but by being a brother of Charles' wife with James referring to William as being his brother-in-law.

Culture

One study, examining the case of envy in the triadic system of sibling, sibling-in-law as well as spouse, concluded that "The sibling-in-law relationship dual-lane similarities with both spousal and sibling relationships" and that "Relational closeness and satisfaction for any relationships in the triad were correlated."

In Islamic law shariʿa and Jewish law halakhah sexual relations between siblings-in-law are prohibited as incestuous, unless the spouse is no longer married. Conversely, in Judaism there was the custom of yibbum, whereby a man had a non-obligatory duty to wed his deceased brother's childless widow so she might realize progeny by him.