What to Call Brother’s Wife? [Answered]

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Inside: If you’ve ever wondered what to call your brothers wife (or your wife’s brother) we cover everything you need to know in this handy explainer.

The point of courtship is for two parties to find out if they get along well enough to take the relationship to the next level.

Often, a partner is not introduced to the family until things get a bit more serious.

Photo showing a group of people on a wedding

First Comes Love, Then Comes Law

Then, the hope is that everyone gets along peacefully and can coexist during family functions from here on out.

As a beloved story about shenanigans surrounding a wedding tells us, “Marriage is what brings us together today. That blessed arrangement, that dream within a dream.”

That feeling of togetherness is the goal for family members. So, in the event that things are as good as they should be, and no one has the means to be derogatory, what’s the technical term for your brother’s wife?

A Spouse is Born

An in-law is someone you’re related to by marriage.

Once your brother is legally married, the woman he’s with is no longer called a girlfriend or fiancé. No, she has an official government-sanctioned title now. Meet your sister-in-law.

If all continues to go well, she’s going to be in your life for quite some time, so it’s best to keep things pleasant. You may even refer to her as a sister if the relationship is warm enough and all parties are comfortable.

A Brother’s Wife

Now that your brother has a wife, she might also be referred to as an aunt one day. She may not be one of the blood relatives, but she will be deeply connected to all of the family members.

A sister-in-law has the potential to have a massive impact on the family as a whole when time moves forward.

The Other in-Laws

Photo showing a group of people inside a house talking to each other

We understand that the sister-in-law is the spouse’s sister, but what about the sister’s husband or the husband’s brother’s wife? It would be easy to get twisted up in terms.

So, let’s go through it together. Below are some commonly used phrasing that could get confusing.


A brother-in-law is essentially a spouse’s brother, the male spouse of a sibling. For example, “Dan is my brother-in-law, he married my older sister Elizabeth.”


This is the father of a spouse. This can refer to both a biological dad or a stepfather.

He would also be the son of a grandfather-in-law, but that’s not necessarily a term that’s used a lot. The same applies to uncle-in-law.

It’s not really used but that would be correct usage.


The mother of the spouse may not necessarily be in a relationship with the father-in-law anymore, but they are still represented as in-laws. Again, this can extend to the stepmother.


If your child marries a man, that man is your son-in-law. Female siblings to the son or the female spouse of your child would be called daughter-in-law.

What do you call your wife’s sister?

As terms mesh, they can get more complicated. Here are a few of the more tricky ways of referring to siblings or other family of your wife or husband:

  • A wife’s brother’s wife will be your sister-in-law, which is the same as saying your brother-in-law’s wife will be your sister-in-law.
  • A co-brother or co-sister-in-law would also be a way to refer to a brother or sister-in-law.
  • One’s husband’s brother’s wife is yet another way of saying sister-in-law.
  • A sister’s husband is called a brother-in-law.
  • Either side’s brother’s wife is called a sister-in-law.

All in the Family

At the end of the day, whether it’s a sister-in-law, daughter, wife, co-sister-in-law, wife’s brother’s wife, or even the wife’s brother, it all boils down to one thing.

No matter what designated phrase you use to refer to someone, married or born, they are all family.

It’s a dual meaning to call someone an in-law. The in-law addition to the words is really just a formal and legal acceptance of a new person.


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About GYAdmin

Hi, I’m Emma. I fell in love with genealogy the second I found out my ancestor fell off the Mayflower. I started GenealogyYou to help others on this fascinating journey (and to put my History degree to some use).