What is a third cousin?
Third cousins share a set of great-great-grandparents. Your parents are second cousins to their parents.
- Shared ancestor
- 4 generations up from you
- They call you
- their third cousin
- Average shared DNA
- ≈ 0.781%
- Cousin number · removed
- 3 · 0
How third cousins connect
Go back four generations: you, your parent, your grandparent, your great-grandparent, and then their parents are the great-great-grandparents you share. Each extra shared generation adds one to the cousin number, so sharing great-great-grandparents makes you third cousins.
Shared DNA
About 0.78% on average, around 75 centimorgans in the Shared cM Project. Roughly one in ten third cousins shares no detectable DNA with you, which is why a missing match does not disprove a documented link.
Why you have so many
Most people have dozens to well over a hundred third cousins, because the number of cousins multiplies with every generation you go back. Many of them turn up as matches on DNA test sites.
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 third cousin
- Expected shared DNA
- ≈ 0.781%
- Degree (civil / canon)
- 8 / 4
- Also called
- 3rd cousin
Why a third cousin?
You share great-great-grandparents. You are 4 generations below them; the other person is 4 generations below them.
The cousin number comes from whoever is closer to the shared ancestor: 4 generations down, minus 1 = third cousin.
You are the same number of generations down, so there is no "removed".
Questions people ask
Are third cousins related?
Yes. They share great-great-grandparents, though they share under 1% of their DNA on average.
What is my third cousin's child to me?
Your third cousin once removed.