By Sanjay Bhagia · 1 November 2026
Most people know who their first cousins are. After that it gets hazy. Is your mother's cousin your second cousin? (No.) What does "removed" mean? Once you know one simple idea, the rest follows: find the ancestor you share, and count the generations.
What is a first cousin?
Your first cousins are your aunts' and uncles' children. You share a set of grandparents, but not parents. You and your first cousin are both grandchildren of the same people.
What is a second cousin?
Your second cousins share your great-grandparents, but not your grandparents. They're the children of your parents' first cousins. You're both great-grandchildren of the same couple.
Third cousins share great-great-grandparents, and so on. The rule: if you and the other person are the same number of generations from your shared ancestor, count those generations and subtract one. Grandchildren (2) are first cousins. Great-grandchildren (3) are second cousins. Great-great-grandchildren (4) are third cousins.
What does "once removed" mean?
"Removed" means you're in different generations. "Once removed" is one generation apart, "twice removed" two.
To work it out, look at the person who is fewer generations from the shared ancestor. Their cousin number gives the cousin part. The difference in generations gives the "removed" part.
- Your first cousin's child is your first cousin once removed.
- Your parent's first cousin is also your first cousin once removed. The relationship works both ways.
- Your grandparent's first cousin is your first cousin twice removed.
- Your second cousin's child is your second cousin once removed.
A common mix-up: your first cousin's child is not your second cousin. But your child and your first cousin's child are second cousins to each other, because they're the same generation.
A cousin chart
Find how you're descended from the shared ancestor down the side, and how the other person is descended across the top. Where they meet is what that person is to you.
| You are the ancestor's… | They: child | They: grandchild | They: great-grandchild | They: great-great-grandchild |
|---|---|---|---|---|
| Child | Brother or sister | Nephew or niece | Great-nephew or niece | Great-great-nephew or niece |
| Grandchild | Uncle or aunt | First cousin | First cousin once removed | First cousin twice removed |
| Great-grandchild | Great-uncle or aunt | First cousin once removed | Second cousin | Second cousin once removed |
| Great-great-grandchild | Great-great-uncle or aunt | First cousin twice removed | Second cousin once removed | Third cousin |
For a bigger version, see the cousin chart, or let the relationship calculator work it out from a few questions.
Worked examples
Your grandfather's sister's grandson
The shared ancestors are your grandfather's parents, your great-grandparents. Your grandfather's sister is their child, and her grandson is their great-grandchild. You're a great-grandchild too. Same generation, three steps down: you're second cousins.
Your mother's first cousin
Your mother and her cousin share grandparents: your great-grandparents. Her cousin is their grandchild. You're their great-grandchild. The closer one is a grandchild, so it's a first cousin, and you're one generation apart: first cousin once removed.
Your grandmother's first cousin
They share your great-great-grandparents. Your grandmother's cousin is their grandchild; you're their great-great-grandchild. First cousin, two generations apart: first cousin twice removed.
Your father's cousin's daughter
Your father and his first cousin share grandparents, who are your great-grandparents. His cousin's daughter is their great-grandchild, like you. You're second cousins.
Why does "removed" confuse people?
Because in everyday speech, families often call a cousin's children "second cousins", and a parent's cousin "my cousin". That's not wrong as family language, but it isn't what the terms mean. The key is that cousin numbers only ever change when you count generations to the shared ancestor. Moving down a generation on one side alone doesn't make a new kind of cousin. It adds a "removed".
Age doesn't matter either. In big families, a first cousin once removed can be older than you, if your parent was the youngest child and their cousin the eldest. Generation is about steps in the tree, not birthdays.
Great-aunt or grand-aunt?
Both mean the same thing: the sister of one of your grandparents. "Great-aunt" is what most people say. Some genealogists prefer "grand-aunt", because it lines up with "grandparent": your grandparent's sister is your grand-aunt, just as your grandparent's mother is your great-grandmother.
Going the other way, your brother's grandchild is your great-nephew or great-niece, also called grandnephew or grandniece. Each generation further adds a "great": your great-grandparent's sister is your great-great-aunt, or great-grand-aunt.
What is a half-cousin?
Half-siblings share one parent instead of two. Their children are half first cousins: they share one grandparent, not a couple. The same goes further out. If the shared ancestor is one person rather than a couple, add "half": half second cousin, half first cousin once removed. In everyday speech most families just say "cousin", and that's fine.
What are double cousins?
When two brothers marry two sisters, or a brother and sister from one family marry a sister and brother from another, their children are double first cousins. They share both sets of grandparents, not one.
What about in-laws and step-relatives?
In-laws are related by marriage, not by descent. Your sister-in-law is your husband's or wife's sister, or your brother's wife. Your cousin's husband isn't your cousin by blood; people often call him a cousin-in-law, though it isn't a formal term. Step-relatives come through a parent's marriage: your stepmother's children are your stepbrothers and stepsisters.
Many families also use "cousin" loosely, for anyone of roughly your generation who's related somehow. In Indian English, "cousin brother" and "cousin sister" are common. And many languages have separate words for relatives English lumps together. Our list of relationship names covers some of them.
How do you work out a relationship quickly?
- Find the closest ancestor (or couple) you both descend from.
- Count how many generations down each of you is: child is 1, grandchild 2, and so on.
- If one of you is 1 generation down, it's a brother, sister, aunt, uncle, niece or nephew, with "great"s added.
- Otherwise, take the smaller number and subtract one: that's the cousin number.
- The difference between the two numbers is how many times removed.
In a family tree you've already built, you don't need to count. Kumbaa's "How are we related?" takes any two people in your family's private archive and names the relationship, with the path spelled out, like "Callum's mother's brother's daughter". For a one-off question, the free relationship calculator does the same without an account.