What "removed" means
Cousin names have two parts. The number (first, second, third) tells you how far back your shared ancestor is. "Removed" tells you how many generations apart you are from each other.
Your first cousin is in your generation: you share grandparents. Their child is one generation below you, so they're your first cousin once removed. Their grandchild is two generations below, so twice removed.
It works in both directions. Your mom's first cousin is one generation above you, which also makes them your first cousin once removed. You're their first cousin once removed too. The label is the same from both sides.
The one rule that solves every cousin
Count how many generations each of you is below the shared ancestor. Take the smaller number and subtract one: that's the cousin number. The difference between the two numbers is how many times removed.
| You are the ancestor's… | They are the ancestor's… | Result |
|---|---|---|
| Grandchild (2) | Grandchild (2) | 2 − 1 = first cousins |
| Grandchild (2) | Great-grandchild (3) | First cousins once removed |
| Grandchild (2) | 2nd great-grandchild (4) | First cousins twice removed |
| Great-grandchild (3) | Great-grandchild (3) | 3 − 1 = second cousins |
| Great-grandchild (3) | 2nd great-grandchild (4) | Second cousins once removed |
Don't want to count? The cousin calculator does it for you.
Why your kids and your cousin's kids are second cousins
This trips everyone up. You and your first cousin share grandparents. Your children share great-grandparents, so they're second cousins. But your child and your first cousin are first cousins once removed, because they're a generation apart.
Second cousin once removed
Same idea, one branch further out: your second cousin's child, or your parent's second cousin. You share about 122 cM of DNA on average, about 1.5%.
How much DNA do you share?
| Relationship | Average cM | Typical range |
|---|---|---|
| First cousin | 866 | 396–1,397 |
| First cousin once removed | 433 | 102–980 |
| First cousin twice removed | 221 | 33–471 |
| Second cousin once removed | 122 | 14–353 |
Source: Shared cM Project v4. Notice the overlap: 230 cM could be a second cousin or a first cousin twice removed. Age usually tells you which.
What do people actually call them?
Mostly just "cousin." Plenty of families call a parent's first cousin "aunt" or "uncle" out of respect. The formal terms matter when you're building a family tree, reading a DNA match list, or, occasionally, checking whether a relationship is legal.
Can you marry a first cousin once removed?
In most US states, yes. You share half as much DNA as first cousins, and the extra genetic risk for children is lower. A handful of states ban marriage between people "nearer of kin than second cousins," which can include first cousins once removed. Check your state.