Calculating Cousin Relationships for Genealogical Research

by Mary Harrell-Sesniak

Next time you attend a family reunion, you're sure to get acquainted with relatives like your first cousin's children or Grandpa's first cousin. How do you calculate these relationships? Are they cousins or removed cousins?

When someone is a “removed” cousin, it indicates that they were born into a different generation than yourself. So in both of these cases, the individuals would be removed cousins. Your cousin's children were born into the generation after yourself, so they are first cousins once removed. And Grandpa's first cousin was born into his generation, which is two removed from yourself, so he/she would be your first cousin twice removed.

Another way to calculate relationships is to “add for greats” and “subtract for generation spans.” Let me explain.

  • Assuming you are in the same generation as your relative, add one to the number of greats in the common ancestor's title to determine the cousinship.

Since a grandparent has no greats in the title, add 0 + 1 = 1 to determine a 1st cousin relationship.

Since a great-grandparent has 1 great in the title, add 1 + 1 = 2nd cousins.

If you share fourth great-grandparents, then 4 + 1 indicates you are fifth cousins.

Descent from Same Generation

Common Ancestors

# of Greats in Title

Add One




+ 1 =

1st cousins


+ 1 =
2nd cousins

2nd great-grandparents


+ 1 =

3rd cousins

3rd great-grandparents

+ 1 =
4th cousins

4th great-grandparents

+ 1 =
5th cousins

  • If you are not in the same generation, calculate using the first method, and subtract “or remove” the difference from the second person. Remember to start with the earliest generation (e.g., Grandpa from the example).

Luckily, most genealogy programs, such as Family Tree Maker, have tools to calculate relationships. Or you may prefer to use generation charts and calculators. Two useful tools are located on the Barren County, Kentucky, GenWeb website, hosted by RootsWeb. These tools come courtesy of T. W. Parker.

(Posted 12 April 2009. Previously published in RootsWeb Review: 11 February 2009, Vol. 12, No. 2)

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