What is a third cousin once removed?
A third cousin once removed is your third cousin's child, or your parent's third cousin.
- Shared ancestor
- 4 generations up from you
- They call you
- their third cousin once removed
- Average shared DNA
- ≈ 0.391%
- Cousin number · removed
- 3 · 1
Where the numbers come from
Your great-great-grandparents are their 3rd great-grandparents. You are four generations down, they are five. Four minus one is three, so third cousins, and the gap of one generation makes them once removed.
Shared DNA
About 0.39% on average, around 48 centimorgans. Many third cousins once removed share no detectable DNA at all.
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 once removed
- Expected shared DNA
- ≈ 0.391%
- Degree (civil / canon)
- 9 / 5
Why a third cousin once removed?
You share great-great-grandparents. You are 4 generations below them; the other person is 5 generations below them.
The cousin number comes from whoever is closer to the shared ancestor: 4 generations down, minus 1 = third cousin.
The gap between your two generation counts (5 − 4) is 1, so you are once removed.
Questions people ask
What is the shorthand?
3C1R.
Is my parent's third cousin my fourth cousin?
No. Your parent's third cousin is your third cousin once removed. Their children would be your fourth cousins.