brother-in-law

American  

[bruhth-er-in-law] / ˈbrʌð ər ɪnˌlɔ /

noun

brothers-in-law plural

1. the brother of one's spouse.

2. the husband of one's sister or brother.

3. the husband of one's spouse's sister or brother.

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brother-in-law British  

noun

1. the brother of one's wife or husband

2. the husband of one's sister

3. the husband of the sister of one's husband or wife

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Other Word Forms

Noun Inflected Forms

• brothers-in-law
  plural

Etymology

Origin of brother-in-law

First recorded in 1350–1400; Middle English brother in law(e); see origin at brother, in, law ¹; from Middle English in-lawe “in law,” i.e., “a person within the regulation and protection of the law,” based on the prohibition by Roman civil law and, later, Christian canon law, of marriages within four degrees of consanguinity, i.e., up to and including first cousins

Example Sentences

At the hospital outside General Santos, Lourdes Camia said she believed her brother-in-law, who was being treated for a heart attack, was safer outside -- despite the heat.

From Barron's • Jun. 9, 2026

At one point, Spaeny looked over to see her brother-in-law having a heart-to-heart with Melton’s dad.

From Los Angeles Times • May 27, 2026

While the ceremony itself remained private with reportedly just Anderson’s twin sister as a witness and brother-in-law as officiant, the absence underscored how closely the Trump family continues to be scrutinized even in personal milestones.

From Salon • May 23, 2026

When Magyar's brother-in-law, Márton Melléthei-Barna, was named justice minister, the new government was bitterly criticised on social media.

From BBC • May 8, 2026

So I told him about my daughters, and about our house in Peshawar and the veranda my brother-in-law and I are building out in the back.

From "A Thousand Splendid Suns" by Khaled Hosseini

Related Words

• aunt
• cousin
• father
• folk
• mother
• niece
• sibling
• uncle