"What's the plural of brother-in-law?"

The plural of brother-in-law is brothers-in-law.

Definition of brother-in-law:

Brother-in-law is a term used to refer to the husband of one's sibling or the brother of one's spouse. It is a term commonly used in many cultures around the world and is often included in family trees and genealogy charts.

When it comes to discussing multiple brothers-in-law, many people may wonder what the correct plural form of brother-in-law is.

Forming the Plural of Hyphenated Compound Words

The general rule to form the plural of hyphenated compound nouns is to change only the primary noun to its plural form.

This is because the primary noun is the most important part of the noun phrase, and changing it to its plural form creates the appropriate number agreement for the noun phrase as a whole.

For example, in the case of "daughter-in-law", the primary noun is "daughter", so we pluralize it to "daughters-in-law" to indicate that there are multiple daughters in law. 

Similarly, in the case of "editor-in-chief", the primary noun is "editor", so we pluralize it to "editors-in-chief" to indicate that there are multiple editors in chief.

In the case of "light-year" however, the primary noun is "year", so the plural form is "light-years" as the second word is pluralized.

This is why the plural of “brother-in-law” is “brothers-in-law” since the primary noun is “brother”.

In summary, the plural form of brother-in-law is brothers-in-law. This term refers to the husbands of one's siblings or the brothers of one's spouse. Using the correct plural form is important when discussing family relationships and helps to avoid confusion when talking about multiple brothers-in-law.

Plural of Brother-in-law Example Sentences

Here are three example sentences each of the singular and plural forms of brother-in-law:


  1. My brother-in-law is coming to visit us next week.
  2. Jane's sister got married last year, and now she has a new brother-in-law.
  3. Mark and his brother-in-law went golfing together on Sunday.


  1. My brothers-in-law are all coming to our family reunion this year.
  2. Jane has two brothers-in-law, one from her husband's side and one from her sister's.
  3. Mark and his brothers-in-law are planning a fishing trip for next summer.

Similar Questions

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The plural of brother-in-law is brothers-in-law
The plural of brother-in-law is brothers-in-law