What is a first cousin?
A first cousin is the child of your aunt or uncle. You share a set of grandparents, and you sit in the same generation.
- Shared ancestor
- 2 generations up from you
- They call you
- their first cousin
- Average shared DNA
- ≈ 12.5%
- Cousin number · removed
- 1 · 0
The relationship in one line
Your parent and their parent were siblings. That makes the two of you grandchildren of the same couple, two generations down on each side, which is what "first cousin" means. When people say just "cousin", this is the relationship they usually have in mind.
Shared DNA
First cousins share about 12.5% of their DNA on average, around 870 centimorgans in the Shared cM Project, with a typical range of roughly 400 to 1,400 cM. That overlaps with other relationships such as great-aunt, half-uncle and great-grandparent, so a DNA match alone rarely proves a first-cousin link.
First cousins in the law
Rules differ widely. First-cousin marriage is legal in the UK, Canada and much of Europe; in the US it is allowed in some states, allowed with conditions in others and banned in the rest, so check your state's current statute.
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 the difference between a first and second cousin?
First cousins share grandparents. Second cousins share great-grandparents, one generation further back.
What is my first cousin's child to me?
Your first cousin once removed.
What are double first cousins?
Cousins whose parents are two pairs of siblings, for example two brothers who married two sisters. They share both sets of grandparents and about twice the usual DNA.