A result of 193 cm from 100 year old, matched up to a 35 yo. Does the age of the participants factor in? The sample also showed cross match. The relationship is estimated at 2nd to 3rd cousins. Does that mean i should be able to locate a common ancestor easier?


Age has no effect on the cM readings. If a person is 10 or 100, it won't result in higher or lower than expected cM values.

But an age difference does affect the possible relationships. Second and Third cousins are on average at the same age. Once removed from that means one cousin is a generation removed. Twice removed means two generations removed. With a 65 year difference, you are looking at likely a difference of 2 or 3 generations between the two.

A second cousin is expected to share the same amount as a first cousin twice removed. A third cousin is expected to share the same amount as a second cousin twice removed.

So factoring the age difference of 65 years, the estimated relationship given as 2nd to 3rd cousins should be thought of as one of:

  • First cousin, twice removed
  • First cousin, three times removed
  • Second cousin, twice removed
  • But keep in mind that generations can be way off between different branches of a family: my father-in-law was thirty years younger than his first cousin, resulting in second cousins 43 years apart in the next generation. A 65-year age difference rules out parent-child, but is only a guideline for more distant relationships. – JPmiaou Sep 11 '19 at 20:31
  • From the Shared cM Project tool, 2C2R is a much smaller likelihood than 1C2R, 1C3R or half-1C2R. This means that the common ancestor you're looking for is likely a grandparent of the 100 y.o. cousin, and likely your great-great-grandparent, or ggg-grandparent. To be certain who the common ancestor is, you'd in theory need both their and your pedigrees extended that far back for all ancestral lines. However, if you have enough shared matches between you with the same ancestors in their trees, you may be able to make an educated guess. – cleaverkin Sep 17 '19 at 20:37

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