What is a cousin-in-law?

Your cousin-in-law is your cousin’s husband or wife, or your husband’s or wife’s cousin. You’re not related by blood: a marriage made you family. The word is less common than brother-in-law, but everyone understands it.

At a glance

Who it is: Your cousin’s spouse, or your spouse’s cousin.
Related by blood?: No. A marriage made you family.
The other way: You’re their cousin-in-law too.

Example familyHannah is married to Noah, Ethan’s first cousin, so she’s Ethan’s cousin-in-law. It works the other way too: Ethan is Hannah’s cousin-in-law.

Hannahyour cousin-in-law

Noahyour first cousin

Anneyour aunt

Thomasyour grandfather

Jamesyour father

You

Ethan

It works from both sides

When your cousin gets married, their husband or wife becomes your cousin-in-law. And when you get married, every one of your spouse’s cousins becomes your cousin-in-law too.

In the example family, it works both ways at once. Sofía married Ethan, so Ethan’s cousin Noah is her cousin-in-law, and Noah’s wife, Hannah, is Ethan’s.

When your cousin and their spouse have children, those kids are your blood relatives: your first cousins once removed, like Noah and Hannah’s little boy, Henry.

Heads-up

One marriage, not two

The name only reaches across one marriage: yours or your cousin’s.

In the example family, Sofía and Hannah married two first cousins, Ethan and Noah. They’re two marriages apart, so the tree has no name for what they are to each other.

And a cousin-in-law isn’t a brother-in-law. Your brother-in-law is your sister’s husband, or your husband’s or wife’s brother. Your cousin’s husband is one branch further out.

The in-law family, by name

All of these are family by marriage, not by blood:

Mother-in-law, father-in-law: your husband’s or wife’s parents.
Son-in-law, daughter-in-law: your daughter’s husband or your son’s wife.
Brother-in-law, sister-in-law: your spouse’s brother or sister, or your brother’s or sister’s spouse.
Grandmother-in-law, grandfather-in-law: your spouse’s grandparents.
Cousin-in-law: your cousin’s spouse, or your spouse’s cousin.
Aunt, uncle: your uncle’s wife or your aunt’s husband. English doesn’t add “in-law” here.
Niece, nephew: your spouse’s nieces and nephews are yours too.
Your child’s in-laws: no single word in English.

Do you have to say “in-law”?

Not at all. After a few holidays together, many families drop the “in-law” and just say “my cousin,” and they mean it.

Cousin-in-law is the word for when you need to be exact: in a wedding toast, on a family tree, or when someone at the party asks how you two are related.

Some families stretch it further and call a cousin’s husband’s sister a cousin-in-law, too. Family words are for bringing people closer, so that’s their call.

In real life

Where cousins-in-law are made

Many cousins-in-law first meet at the wedding. You spend the reception at the cousins’ table, guessing who belongs to which side, and by the last dance you’ve traded numbers and been invited to a Fourth of July cookout.

A few summers later, they’re the one bringing the potato salad and teaching your kids cornhole.