Both of Which vs. Both of Whom – Which is Correct?

The choice between “both of which” and “both of whom” depends entirely on the antecedent: use both of whom when referring to two people, and both of which when referring to two things or animals. Both phrases are grammatically correct when applied appropriately.

Both of Which or Whom – Which is Correct?

Both “both of which” and “both of whom” are grammatically correct phrases, but their usage hinges on the nature of the noun or pronoun they refer back to (the antecedent). The core distinction lies in whether you are referring to people or to things/animals.

• Use both of whom when the antecedent is a person or a group of people. “Whom” is the objective case of “who” and is used when referring to people as the object of a verb or preposition.
• Use both of which when the antecedent is a thing, an animal, or an idea. “Which” is a relative pronoun used for non-human antecedents.

The confusion often arises because both phrases serve to introduce a non-restrictive clause that provides additional information about two previously mentioned entities.

The Best Trick to Remember the Difference

A simple trick to remember the difference is to think of the “M” in “whom” standing for “human.”

• Whom = Human (referring to people)
• Which = Thing (referring to non-human entities)

If you can replace the pronoun with “him” or “them,” use “whom.” If you can replace it with “it” or “them” (for things), use “which.”

Word/Phrase	Part of Speech	Meaning	Example
Both of Which	Relative Pronoun Phrase	Refers to two non-human entities (things, animals, concepts) from a preceding clause.	I bought two books, both of which I finished in a day.
Both of Whom	Relative Pronoun Phrase	Refers to two people from a preceding clause, often as the object of a verb or preposition.	The committee interviewed two candidates, both of whom were highly qualified.

How to Use Both of Which

“Both of which” is a relative pronoun phrase used to introduce a dependent clause that provides additional, non-essential information about two non-human antecedents (things, animals, or abstract concepts). It acts as the object of a preposition (of) within its clause.

Example 1: The company launched two new products, both of which received excellent reviews.

Example 2: She adopted two kittens, both of which quickly adjusted to their new home.

Example 3: He presented two theories, both of which were debated vigorously by the panel.

Etymology of the word Both of Which

The word “both” originates from Old English bāþā, meaning “both, two together,” derived from Proto-Germanic *bē-þō. “Which” comes from Old English hwilc, meaning “of what kind,” tracing back to Proto-Germanic *hwa-likaz. Together, they form a phrase that has evolved to specifically refer to two non-human items in a relative clause.

How to Use Both of Whom

“Both of whom” is a relative pronoun phrase used to introduce a dependent clause that gives extra, non-essential information about two human antecedents. “Whom” functions as the object of the preposition “of” within its clause, referring specifically to people.

Example 1: I met two colleagues today, both of whom are starting new projects next month.

Example 2: The director spoke to two actors, both of whom expressed interest in the lead role.

Example 3: She has two children, both of whom are now attending university.

Etymology of the word Both of Whom

“Both” has its roots in Old English bāþā. “Whom” is the objective case of “who,” originating from Old English hwām, which was the dative case of hwā (“who”). This reflects its historical role in referring to people as the object of a verb or preposition, a function it maintains in the phrase “both of whom.”

Related Concepts

Understanding the broader grammatical concepts behind “which” and “whom” can further clarify their correct usage.

• Relative Pronouns: Words like “who,” “whom,” “whose,” “which,” and “that” that introduce a dependent clause (a relative clause) and connect it to a noun or pronoun in the main clause. They function as either the subject or object within their own clause.
• Antecedents: The noun or pronoun that a pronoun refers back to. Correct pronoun usage (e.g., “whom” for people, “which” for things) depends on identifying the antecedent.
• Subject vs. Object Pronouns: Personal pronouns change form depending on their grammatical role. “Who” is a subject pronoun (like “he,” “she”), while “whom” is an object pronoun (like “him,” “her”). This distinction is crucial for correct usage, especially when a pronoun follows a preposition.

Examples from Media and Literature

• “They had two main characters in the story, both of whom underwent significant personal growth.” (Literary analysis)
• “The company released two major software updates this year, both of which addressed critical security vulnerabilities.” (Tech news)
• “I recall two pivotal scenes from the film, both of which showcased the lead actress’s incredible range.” (Film critique)
• “The scientists studied two rare species of birds, both of which exhibited unique migratory patterns.” (Nature documentary)
• “He introduced me to his two mentors, both of whom have greatly influenced his career path.” (Interview transcript)

Practice Exercises

Choose the correct word to complete the sentence.

1. The two proposals, _____ were submitted last week, are currently under review.
2. She interviewed two applicants, _____ impressed her with their experience.
3. I found two antique vases, _____ were surprisingly well-preserved.
4. He introduced me to his two brothers, _____ I had never met before.
5. The team developed two innovative solutions, _____ aimed to reduce energy consumption.

Answer Key

1. both of which
2. both of whom
3. both of which
4. both of whom
5. both of which

Both of Which Synonyms

Synonym/Alternative	Definition/Context
and both of them (things)	A more informal or direct rephrasing, separating the conjunction and pronoun.
the two of which	Emphasizes the quantity “two” more explicitly.
each of which	Focuses on the individual nature of the two items.

Both of Whom Synonyms

Synonym/Alternative	Definition/Context
and both of them (people)	A more informal or direct rephrasing, separating the conjunction and pronoun.
the two of whom	Emphasizes the quantity “two” more explicitly when referring to people.
each of whom	Focuses on the individual nature of the two people.

Frequently Asked Questions

Question 1: Can I use “both of which” or “both of whom” at the beginning of a sentence?
No, these phrases are relative pronouns that introduce dependent clauses and must refer back to an antecedent in a preceding independent clause. Therefore, they cannot begin a sentence.

Question 2: Is “both of who” ever correct?
No, “both of who” is grammatically incorrect. “Who” is a subject pronoun, while “whom” is an object pronoun. Since “of” is a preposition, it must be followed by an object pronoun, hence “whom.”

Question 3: What if I’m referring to a mix of people and things?
If you are referring to a mixed group (e.g., two people and two things), you cannot use a single “both of which” or “both of whom.” You would need to rephrase the sentence, perhaps by separating the groups or using a more general construction like “all of them.” For example, instead of “I saw two students and two books, both of which/whom…”, you might say “I saw two students and two books; the students were both engaged, and the books were both interesting.”

Conclusion

Mastering the distinction between “both of which” and “both of whom” is a clear indicator of grammatical precision. Remember the simple rule: “whom” for people, “which” for things or animals. By consistently applying this principle, you can ensure your writing is clear, correct, and professional.

Pro Tip: When in doubt, mentally substitute “him/her” for “whom” and “it” for “which” in the clause. If “him/her” fits, “whom” is correct. If “it” fits, “which” is correct. This simple test can help maintain your professional reputation in formal communication.