How are we related?
A relationship calculator for your own family.
Pick any two people in your family tree and see exactly how they are related, from first cousins to in-laws, with the path that connects them.
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How cousin relationships work
Every cousin relationship comes down to two numbers. First, find the most recent common ancestor: the closest person, or couple, that both relatives descend from. Then count how many generations each relative is below that ancestor.
The cousin degree is the smaller of the two counts minus one. If you and a relative are both two generations below your shared grandparents, you are first cousins. If you are both three generations below shared great-grandparents, you are second cousins.
The number of times removed is the difference between the two counts. Cousins in the same generation are not removed at all. When one is a generation further down, they are once removed; two generations, twice removed.
A worked example
Drita is your great-grandmother. You are three generations below her. Your mother’s cousin Arta is her granddaughter, two generations below her. The smaller count is two, so the degree is first; the counts differ by one, so Arta is your first cousin once removed. Arta’s son is three generations below Drita, the same as you, which makes him your second cousin. His daughter is your second cousin once removed.
Cousin chart
| You \ Them | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| 1 | Sibling | Niece or nephew | Great-niece or great-nephew | Great-great-niece or nephew |
| 2 | Aunt or uncle | First cousin | First cousin once removed | First cousin twice removed |
| 3 | Great-aunt or great-uncle | First cousin once removed | Second cousin | Second cousin once removed |
| 4 | Great-great-aunt or uncle | First cousin twice removed | Second cousin once removed | Third cousin |
How to use the relationship calculator
- 01
Build the connecting branches.
Add both relatives and the parents that link them back to a shared ancestor. The calculator works from parent and partner links.
- 02
Pick two people.
Open “How are we related?” and choose the two relatives you are curious about.
- 03
Read the answer and the path.
See the relationship by name, such as “second cousin once removed”, and the chain of people that connects them.
What the calculator can name
Direct line
Parents, grandparents and great-grandparents, counted up to “3rd great-grandmother” and beyond, and the same for children and grandchildren.
Aunts, uncles, nieces and nephews
Including great-aunts, great-great-uncles and great-nieces, and aunts or uncles by marriage.
Cousins of every degree
First, second, third cousins and further, with any number of times removed.
Half relations
Half-siblings who share one parent, and half cousins who descend from only one of the shared ancestors.
Step, adoptive and foster
Stepmothers, stepsons and stepsisters, adoptive parents and adopted children, and foster relations, named as such.
In-laws and partners
Mothers-in-law, brothers-in-law and children-in-law, husbands, wives, partners and ex-spouses.
Why use your own tree instead of a chart
A cousin chart works when you already know the generation counts. In a real family you often don’t: you know someone is “Grandpa’s cousin’s grandson” but not how many steps separate you. The calculator walks the tree for you, finds the shared ancestor and shows each person on the path, so you can check the answer yourself.
It is most useful when the tree is complete enough to connect both people. Ask the relatives who know each branch to help by sharing the tree with them, or bring in earlier research with a GEDCOM import.
Relationship calculator questions
What does “once removed” mean?
“Removed” counts the difference in generations between two cousins. Your first cousin’s child is one generation below your first cousin, so they are your first cousin once removed. Your first cousin’s grandchild is your first cousin twice removed.
What is the difference between a second cousin and a first cousin once removed?
Second cousins are in the same generation and share great-grandparents. A first cousin once removed is one generation apart from you: either your parent’s first cousin or your first cousin’s child.
What is a half cousin?
Half cousins descend from only one person of the ancestral couple. If your grandfather had children with two different wives, the grandchildren from each marriage are half first cousins to each other.
Does the calculator handle in-laws and step-relatives?
Yes. It names in-laws such as a mother-in-law or sister-in-law, step-parents, stepchildren and stepsiblings, adoptive and foster relations, and partners including ex-spouses. It also follows longer paths through a marriage.
Is the relationship calculator free?
Yes. It is part of every family tree on Build a Family Tree, which is free with no paid plans. Add the people and their parent links, then pick any two of them.
Find out how you’re related.
Build your family tree and ask the question at the next family gathering, free.
More ways to build your family tree
- Free family tree maker Build a family tree online with photos, stories and dates. No paid plans.
- Collaborative family tree Invite relatives by email as editors or viewers and build the tree together.
- GEDCOM import and export Move a family tree in or out using a standard GEDCOM file.
- Family tree template Lay out your tree on a canvas, then export it as a PNG or PDF to print.
Or go back to the Build a Family Tree home page.