How to read a cousin chart
Most cousin charts are printed as a grid, which hides the thing that actually determines the answer: descent. This one is drawn as a tree, so the rule is visible. Start at the common ancestor at the top and walk down. Everyone on the same row is the same number of generations from that ancestor, and rows are what the two numbers in a cousin relationship are counting.
- Find the closest shared ancestor. Not any shared ancestor — the most recent one you both descend from. If one of you descends from the other, you are not cousins at all; you are parent, grandparent, or great-grandparent.
- Count down to each person. Child is 1, grandchild is 2, great-grandchild is 3, great-great-grandchild is 4. Count for yourself and for them.
- Cousin number = smaller count − 1. Both at 2 makes first cousins. Both at 3 makes second cousins. Both at 4 makes third cousins.
- Removed = the difference. Counts of 2 and 3 differ by one, so it is "once removed". Counts of 2 and 4 differ by two: twice removed.
The cousin chart as a table
The same rule in grid form. Read one person's distance from the shared ancestor across the top and the other person's down the side.
| Child (1) | Grandchild (2) | Great-grandchild (3) | Great-great-grandchild (4) | |
|---|---|---|---|---|
| Child (1) | Siblings | Aunt / uncle & niece / nephew | Great-aunt / great-uncle | Great-great-aunt / great-great-uncle |
| Grandchild (2) | Aunt / uncle & niece / nephew | First cousins | First cousins once removed | First cousins twice removed |
| Great-grandchild (3) | Great-aunt / great-uncle | First cousins once removed | Second cousins | Second cousins once removed |
| Great-great-grandchild (4) | Great-great-aunt / great-great-uncle | First cousins twice removed | Second cousins once removed | Third cousins |
The diagonal is where cousins of the same degree sit, and every step away from the diagonal adds one "removed". The top-left corner is the case people forget: when the smaller count is 1, there is no cousin relationship at all — that is the aunt, uncle, niece and nephew territory.
What "once removed" actually means
Removal is about generations, not distance or affection. Your first cousin's child is your first cousin once removed. So is your parent's first cousin — the term does not say which of you is older, only that you are one generation apart on the tree. This is why family reunions produce so many arguments: the same label is correct pointing up and pointing down.
The chart above shows both directions at once. Going down the left branch you reach "first cousin once removed" as the child of your first cousin. Going down the right branch you reach it as your parent's first cousin, one generation above your second cousin.
Building your own cousin chart
Swap the role names in the outline for real ones. The structure is what carries the relationships, so as long as each person sits under the parent they descend from, the labels can say anything.
- Start from the shared ancestor, not from yourself. A cousin chart is a descent tree. Putting yourself at the root gives you an ancestor chart instead, which answers a different question.
- One indent per generation, always. Skipping a generation to save space breaks the counting rule the whole chart depends on.
- Put spouses on the same line.
George & Marykeeps the couple together without adding a generation. - Go left-to-right for deep families. Five or more generations fit a page better sideways — one click on the layout toggle.
- Tab and Shift+Tab move a person and their descendants together, so re-attaching a whole branch to a different parent is two keystrokes.
How much DNA cousins share
Averages, because recombination makes the real figure vary between siblings: first cousins share about 12.5% of their DNA, second cousins about 3.13%, and third cousins about 0.78%. The drop is steep enough that beyond third cousins a DNA test often cannot tell you the exact relationship — it gives a range, and a paper chart like this one is what resolves it.
Frequently asked questions
What is a first cousin once removed?
Your first cousin's child, or your parent's first cousin. “Removed” counts generations, not closeness: one removed means the two of you sit one generation apart on the family tree. Your first cousin's child is your first cousin once removed, and so is your parent's first cousin — the relationship is the same in both directions.
How do I work out what cousin someone is?
Find the closest ancestor you both descend from. Count the generations from that ancestor down to you, and down to them. Take the smaller of the two counts and subtract one — that is the cousin number. The difference between the two counts is how many times removed. Both grandchildren of the same ancestor: 2 minus 1 equals first cousins, no removal.
What is the difference between a second cousin and a first cousin once removed?
Second cousins are in the same generation as each other and share a great-grandparent. A first cousin once removed is in an adjacent generation and shares a grandparent with one of you. People mix these up constantly because both involve three generations somewhere in the count — the test is whether you and the other person are the same distance from the shared ancestor.
Are second cousins blood related?
Yes. Second cousins descend from the same great-grandparents and share roughly 3.13% of their DNA on average, compared with about 12.5% for first cousins. Third cousins share around 0.78%, which is why DNA testing services often cannot distinguish a third cousin from a more distant match.
For a broader chart of a whole family rather than the cousin lines specifically, the family tree diagram maker uses the same outline and loads a three-generation preset. The tree diagram maker is the general version of the engine, the hierarchy chart maker applies it to organisations instead of families, and the examples gallery opens every preset in the editor with one click. For medical history and the standard clinical symbols, that is a genogram — a genogram maker handles those conventions properly.