tools guide
Family relationship calculator — cousin math without the headache
Short answer
A family relationship calculator turns two people and a common ancestor into a labeled relationship — second cousin, once removed, half-uncle, and so on. The math is simple once you can spot the most recent common ancestor. Print the reference table below or use the interactive calculator (coming soon) for edge cases.
- Nth cousin = generations to shared ancestor (whichever is lower).
- 'Removed' = the difference in generations between the two people.
- 'Half' = shares one biological ancestor instead of two.
- 'In-law' = created by marriage, not by blood.
This guide is being expanded. In the meantime, the linked pages below and the FAQ answer the questions readers most often send us. If yours isn't here, write the desk and we'll add it in the next revision.