What is a second cousin?
Short answerYour second cousin is the child of your parent’s first cousin: you share a set of great-grandparents. It works the same both ways: you are their second cousin too. Full second cousins share about 3.12% of their DNA on average.
The family line, drawn out
Follow the highlighted line from you up to the shared ancestor and down to them.
How to work it out
- Find the nearest ancestor you share: your great-grandparent.
- Count the generations from each of you up to that ancestor: 3 for one, 3 for the other.
- Take the smaller number and subtract one: 3 − 1 = 2, so they are second cousins.
- The difference between the two numbers is how many times removed: 3 − 3 = 0 (not removed).
Cousins are only “removed” when they belong to different generations. Two people in the same generation are never removed, whatever their ages.
Their family and yours
Relationships shift by one step for each generation. Here is how the people around them relate to you:
| Their child | second cousin once removed |
| Their parent on the shared line | first cousin once removed |
| Your child sees them as your child’s | second cousin once removed |
| Your parent sees them as your parent’s | first cousin once removed |
| What they call you | second cousin |
Shared DNA
On average, full second cousins share about 3.12% of their DNA. That figure is the expected value: it halves with every generation of separation, and real amounts vary from person to person. A half relationship (through only one shared ancestor instead of a couple) shares about half as much: 1.56%.
Let Family Trees name it for you
In Family Trees, open anyone’s page to see how they are related to you in plain words, or choose any two people under How are they related?. The app counts the shortest blood line through birth and adoptive parents, names step, foster and in-law relations too, and uses exactly the words on this page. It’s free for a family of up to 100 people. You can also try the relationship calculator here.
Questions
What is a second cousin?
Your second cousin is the child of your parent’s first cousin: you share a set of great-grandparents. It works the same both ways: you are their second cousin too.
How much DNA do you share with a second cousin?
About 3.12% on average. Each generation of separation halves the expected amount, and individual results vary.
What is my second cousin’s child to me?
Your second cousin once removed.