How cousin relationships actually work
Almost every family has had the conversation. Someone says "second cousin," someone else says "first cousin once removed," a third person insists they're the same thing — and nobody can quite explain why. The good news is that every cousin relationship follows one simple rule, and once you've seen it you'll never need to guess again.
The rule: find the closest ancestor you and the other person both come from. Count how many generations down it is to each of you. The smaller of the two numbers tells you what kind of cousin you are. The difference between them tells you how many times "removed."
What "first," "second" and "third" mean
The number is about how far back your shared ancestor sits. If you share a set of grandparents, you're first cousins. Share great-grandparents and you're second cousins. Share great-great-grandparents and you're third cousins, and so on up the tree. Each step further back adds one to the number.
What "removed" means
"Removed" simply means you're on different generations. Your mom's first cousin is one generation above you, so she's your first cousin once removed. Your first cousin's daughter is one generation below you — and she's also your first cousin once removed. The phrase works the same in both directions, which is why two people can call each other by the exact same name even though one is decades older.
If the calculator above ever gives you an answer that feels backwards, this is usually why. There's a longer explanation in what "once removed" means.
A cousin chart you can read at a glance
Pick how you're related to the shared ancestor down the left side, then how the other person is related to them along the top. Where the row and column meet is your answer.
| Shared ancestor is your… / their… | Grandparent | Great-grandparent | 2x great-grandparent | 3x great-grandparent |
|---|
| Grandparent | First cousin | First cousin once removed | First cousin twice removed | First cousin three times removed |
|---|
| Great-grandparent | First cousin once removed | Second cousin | Second cousin once removed | Second cousin twice removed |
|---|
| 2x great-grandparent | First cousin twice removed | Second cousin once removed | Third cousin | Third cousin once removed |
|---|
| 3x great-grandparent | First cousin three times removed | Second cousin twice removed | Third cousin once removed | Fourth cousin |
|---|
Want this on paper for a reunion or a school project? There's a printable version, and a step-by-step guide to reading a cousin chart.
The questions people ask most
- What is my cousin's child to me? Your first cousin once removed — not your second cousin, which is the most common mix-up. Here's why.
- What are my kids and my cousin's kids to each other? Second cousins. They're on the same generation and share your grandparents as their great-grandparents.
- What is my mom's or dad's cousin to me? Your first cousin once removed, the same as your cousin's child, just in the other direction.
- What is my grandma's sister to me? Your great-aunt, sometimes called a grandaunt. More on great-aunts and great-uncles.
- Is a second cousin the same as a first cousin once removed? No, and the difference trips up almost everyone. See the two side by side.
If your question isn't here, the calculator above handles any combination — tap one of the common questions, or use the + and − buttons to build the exact relationship you're wondering about.
Half, step and double cousins
Half cousins share just one grandparent rather than a couple — for example, when your parent and their parent are half-siblings. You're related by blood, just a little less closely than full cousins. More about half cousins.
Step cousins aren't related by blood at all. They become family through a marriage, when a parent or aunt or uncle marries someone who already has children. How step cousins work.
Double cousins happen when two siblings from one family marry two siblings from another. Their children share both sets of grandparents, so they end up about as closely related as half-siblings. Double cousins, explained.
Relatives by marriage have their own names, too — your cousin's wife, your aunt's husband, your child's in-laws. The in-law relationship chart covers those.
How much DNA do cousins share?
If you've taken a DNA test, your matches are usually shown in centimorgans (cM), a measure of how much DNA two people share. Closer relatives share more, but the amount varies quite a bit from one pair of cousins to the next, so treat these as rough averages rather than exact numbers.
| Relationship | Average shared DNA | Roughly |
|---|
| First cousin | about 12.5% | around 866 cM |
|---|
| First cousin once removed | about 6.25% | around 433 cM |
|---|
| Second cousin | about 3% | around 229 cM |
|---|
| Third cousin | under 1% | around 73 cM |
|---|
By third and fourth cousins the numbers get small enough that some real cousins share no DNA a test can pick up at all — that doesn't mean you're not related. If you have a match and want a likely relationship, try the DNA match calculator, or see the full shared cM chart.
Quick answers
Does "removed" go up or down?
Both. It only tells you there's a generation gap, not which way. Your parent's cousin and your cousin's child are both your first cousins once removed.
Are second cousins related by blood?
Yes. Second cousins share a set of great-grandparents, so they're blood relatives — just further back than first cousins.
What's the difference between a great-aunt and a grandaunt?
Nothing — they're two names for the same relative, your grandparent's sister. "Grandaunt" is the more precise term, but "great-aunt" is what most families say.
Can the calculator handle relatives by marriage?
Yes. Choose "step" or "marriage" in the builder above to see how the relationship is named when someone joins the family through a marriage.
Do my family's names or photos get uploaded?
No. Everything happens in your own browser. Names and photos you add to a chart never reach our servers, and they're gone when you close the page unless you download your chart.
