Feel like you need a calculus equation to figure out exactly how you’re related to cousin so-and-so from your mom’s great-grandmother’s brother’s line? Let us simplify things.

What kind of cousins you are depends on the most recent ancestor you share with your relative. First cousins share grandparents. Second cousins share great-grandparents, third cousins share great-great-grandparents, and so on. Add a “great” for each generation away from the common ancestor.

Things get trickier when you’re talking about removed cousins. Each “removal” signifies one generation of difference between the two cousins. Your first cousin’s child is your first cousin once removed. Your first cousin’s grandchild is your first cousin twice removed. For example, Ann and Bea, who met at a genealogical society meeting, should follow these steps to determine their cousin relationship:

1. Identify the most recent ancestor. For Ann and Bea, let’s say it’s James Eugene Harding, born in 1850.

2. Determine each cousin’s relationship to that ancestor. Ann and Bea determined that James is Ann’s great-great-grandfather and Bea’s fourth-great-grandfather.

3. “Equalize” the cousins at the level of the one closest to the common ancestor. Equalizing the cousins at Ann’s level would make them third cousins.

4. Add one “removed” for each difference in generations between the cousins. Two “greats” separate Ann and Bea—they’re third cousins twice removed.

Still confused? Download our free PDF relationship chart or use the cousin calculator.

From the May/June 2015 Family Tree Magazine