Family Relationship Calculator

Genealogists describe how two people relate by counting generations up to their most recent common ancestor (MRCA). Each step up is one generation: parent = 1, grandparent = 2, great-grandparent = 3, and so on. Both people must share that exact ancestor — not just the same surname or hometown.

When both people are the same number of generations from the MRCA, they are nth cousins where n = generations minus one. Same grandparent → 1st cousins; same great-grandparent → 2nd cousins. When the counts differ, add "once removed," "twice removed," and so on for each extra generation on one side only.

With the default inputs — 3 generations for Person A and 3 for Person B — both of you reach a shared great-grandparent at the same depth. Three minus one gives cousin degree 2, and because the counts match there is no removal. The calculator labels that relationship as 2nd cousin.

Removal describes an asymmetry. If Person A is 2 generations up (grandparent level) and Person B is 3, you get 1st cousin once removed — one side sits a generation closer to the shared ancestor. Parent–child pairs (1 and 2) produce aunt/uncle or niece/nephew labels instead of cousin math.

This chart covers blood-line cousin relationships from a shared ancestor. Step-siblings, in-laws, adoption without shared biology, and half-siblings need family context the generation count alone cannot capture. Treat the output as a genealogy shorthand, not legal kinship proof.

Worked examples beyond the defaults: both at 2 generations → 1st cousins (shared grandparent). Both at 4 → 3rd cousins. Person A at 2 and Person B at 4 → 1st cousin twice removed. Use the ancestor count calculator to see how many direct ancestors sit at each depth.

DNA testing companies sometimes report "4th–6th cousin" ranges that do not line up exactly with paper genealogy when pedigree collapse or unknown branches exist. This tool assumes you already know the correct generation count to the documented MRCA.