tools guide
Family relationship calculator — cousin math without the headache
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.
How to use this guide in real research
Begin with a specific person, place, and approximate date rather than a name alone. Record the repository, collection, image or certificate number, and access date for every result. That citation lets another researcher retrace the same evidence and helps you distinguish people who share a name.
Treat indexes and transcriptions as finding aids. Whenever possible, open the original image and compare names, ages, relationships, locations, and informants with records you already trust. A plausible match becomes a supported conclusion only when independent sources agree and conflicting evidence has been addressed.
Quality checks before adding a conclusion
- Search spelling variants, initials, nicknames, neighboring households, and a wider date range.
- Prefer records created close to the event, while noting who supplied each fact.
- Keep negative searches and rejected matches in your research log so work is not repeated.
- Mark uncertain relationships clearly until multiple independent records support them.