What is a cousin-in-law?
A cousin-in-law is either your spouse's cousin or your cousin's husband or wife. There is no blood relationship; you are connected through a marriage.
- Shared ancestor
- 2 generations up from you
- They call you
- their first cousin
- Average shared DNA
- ≈ 12.5%
- Cousin number · removed
- 1 · 0
Is cousin-in-law a real thing?
Yes, in everyday use. Dictionaries such as Merriam-Webster list only a handful of formal in-law terms: mother-, father-, son-, daughter-, brother- and sister-in-law. "Cousin-in-law" extends the same pattern and is understood by everyone, even if it has no legal standing.
The two versions
Your spouse's cousin: your partner's first cousin becomes your cousin-in-law when you marry. Your cousin's spouse: when your cousin marries, their husband or wife becomes your cousin-in-law. Some people add "by marriage" instead: "my cousin by marriage".
Use the calculator
In the calculator's Step by step mode, tick "Start from my spouse" to name any relative of your partner, or "End with that person's spouse" to name someone who married into your family.
Check your own relative
Not sure this is the right term? Enter your actual connection.
Find the most recent ancestor you both descend from, then say how each of you is connected to them.
- They call you
- their first cousin
- Expected shared DNA
- ≈ 12.5%
- Degree (civil / canon)
- 4 / 2
- Also called
- 1st cousin
Why a first cousin?
You share grandparents. You are 2 generations below them; the other person is 2 generations below them.
The cousin number comes from whoever is closer to the shared ancestor: 2 generations down, minus 1 = first cousin.
You are the same number of generations down, so there is no "removed".
Questions people ask
What is my cousin's wife to me?
Your cousin-in-law, or cousin by marriage.
What is my husband's cousin to me?
Your cousin-in-law.
What is my cousin-in-law's child to me?
If it is your cousin's child, they are your first cousin once removed by blood. If it is your spouse's cousin's child, they are your spouse's first cousin once removed and related to you by marriage.