What is a second cousin once removed?
A second cousin once removed is your second cousin's child, or your parent's second cousin. You are second cousins, separated by one generation.
- Shared ancestor
- 3 generations up from you
- They call you
- their second cousin once removed
- Average shared DNA
- ≈ 1.56%
- Cousin number · removed
- 2 · 1
Where they sit on the tree
In the downward version, your great-grandparents are their great-great-grandparents. You are three generations below the shared couple, they are four. The smaller number, three, minus one gives "second"; the difference of one gives "once removed".
In the upward version, your parent's second cousin shares your great-great-grandparents: four generations above you and three above them.
Shared DNA
Around 1.6% on average, roughly 120 centimorgans, according to the Shared cM Project, though some pairs share no detectable DNA at all.
Talking about it
At a reunion, "my mum's second cousin" is clear to everyone. On a genealogy chart, write "2C1R", the standard shorthand used by DNA testing 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 second cousin once removed
- Expected shared DNA
- ≈ 1.56%
- Degree (civil / canon)
- 7 / 4
Why a second cousin once removed?
You share great-grandparents. You are 3 generations below them; the other person is 4 generations below them.
The cousin number comes from whoever is closer to the shared ancestor: 3 generations down, minus 1 = second cousin.
The gap between your two generation counts (4 − 3) is 1, so you are once removed.
Questions people ask
What is my second cousin once removed's child to me?
If they are your second cousin's grandchild, they are your second cousin twice removed. If the person is your parent's second cousin, their child is your third cousin.
What does 2C1R mean?
It is shorthand for second cousin once removed, used on Ancestry, 23andMe and in genealogy notes.