What are double cousins?
Double cousins are related through both of their parents. The classic case: two brothers marry two sisters, and their children are double first cousins.
- Shared ancestor
- 2 generations up from you
- They call you
- their first cousin
- Average shared DNA
- ≈ 25%
- Cousin number · removed
- 1 · 0
Why "double"
Normal first cousins share one set of grandparents. Double first cousins share both sets, because each of their parents is a sibling of one of the other child's parents. They are cousins twice over, on the mother's side and on the father's.
Shared DNA
About 25% on average, twice the usual first-cousin figure and in the same range as a half-sibling or grandparent. This regularly surprises people on DNA test sites.
How common is it?
It was more common in small rural communities and in families where siblings married into the same family. It still happens today, and the term also covers double second cousins and other doubled links.
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
Are double cousins like siblings genetically?
Not quite. Full siblings share about 50% of their DNA; double first cousins about 25%.
Do double cousins have the same grandparents?
Yes, all four grandparents are shared.