Figuring Out Family Trees

Stupid Question ™
June 13, 2002
By John Ruch
© 2002

Q: How do you figure out all that “third cousins, twice removed” stuff? And are there cousins from different generations?
—D.R.


A: Yes, you can (and surely do) have cousins from different generations; in fact, that’s what the “removed” means.

This is horribly confusing because of the imprecision of genealogical terms and the difficulty of imaging the geometric progression of a family tree.

A cousin is basically any relative who shares a common ancestor with you, but is not your brother or sister. In the broadest genetic sense, we’re all cousins, which shows you how vague the word can be.

In genealogy, “cousin” is used more strictly to define the relationship between offspring of any one ancestor (and is not applied to nephews/nieces). Thus, the relation between you and your great-grandmother is great-grandparent/grandchild, not cousins. But the relation between you and your great-grandmother’s grandchild is cousin/cousin.

All the “firsts” and “thirds” and “removeds” get tacked on to define the degree of distance between cousins, both within a generation and between generations.

The “first,” “second,” etc. system counts the number of generational steps cousins are from their common ancestor. Thus, the children of a brother and sister are first cousins to each other—they’re all one step away from the common grandparents. The children of those first cousins are second cousins to each other. And so on.

Another way to think about it: A relative who shares two of your grandparents is your first cousin. One who shares great-grandparents is your second cousin. One who shares great-great-grandparents is your third cousin. And so on.

“Removed” means you and your cousin are from different generations. “Once removed,” “twice removed,” etc. are used to count the generational steps separating the cousins. The closest “removed” cousin you can have is your first cousin, once removed. That’s the child of one of your grandparent’s siblings.

To put it another way: Your mother’s first cousin (mutual grandchildren of common ancestor) is your first cousin, once removed. (They’re the grandchild and you’re the great-grandchild.) Your grandmother’s first cousin is your first cousin, twice removed. And so on through 20th cousins, 40 times removed or whatever becomes necessary.

Your hypothetical “third cousins, twice removed” is the relationship between the great-great-grandchild and the great-great-great-great-grandchild of a common ancestor.

Got all that? If so, you’re a better person that I. The whole cousin thing is really a math problem that gets confusing when you try to describe it in words.

It’s not helped by vernacular uses of “cousin.” Up until around 1800 it was common to use “cousin” to refer specifically to nephews/nieces, which we definitely don’t do anymore. And first cousins, once removed are often casually referred to as “second cousins.”

The best way to get a handle on the cousin mess is to map the relationships out on a chart. A simple and easy-to-read example can be found in the youth-oriented book “Do People Grow on Family Trees?” by Ira Wolfman.