So … Is He My Second Cousin or My First Cousin Once Removed???

I’ve been talking to a friend who is a fifth cousin once removed. “How on earth,” she said, “do you determine our relationship?” I mumbled something incoherent about “rules” concerning degrees of consanguinity before concluding it was impossible to explain without visual aids.

Most of you undoubtedly figured out long ago how to tell a fourth cousin from a fifth cousin, and what “once removed” and “twice removed” mean. It took me a while to get to an “AHA!” moment on those issues. If this stuff is old hat for you, please head for this website’s archives and find an article about genealogical proof, or legal concepts in family history research, or the Scots-Irish.  If you have had any trouble calculating consanguinity, please read on.  There WILL be visual aids.

OK, we all know how to identify a first cousin, right? He, or she, is a child of one of your parent’s siblings, and you share a set of grandparents. The chart below shows a pair of Rankin first cousins, Tom and Robert (the green rectangles), grandsons of John Rankin and Emma Brodnax. Please note: John and Emma, my grandparents, are the only real people on the charts in this article. All others are fictional.

Please notice that there is one generation in between the first cousins, Tom and Robert, and their common ancestors, John and Emma.

OK, moving on, let’s add a generation: Chris and Alex, sons of Tom and Robert, respectively – the green rectangles in the chart below. Chris and Alex are second cousins. Note that there are two generations between the second cousins and their common ancestors, John and Emma.

This demonstrates the general rule: the number of generations between the youngest members of the line and their common ancestors equals the degree of consanguinity. Like so …

  • One generation between the youngest & the common ancestors = first cousins
  • Two generations between the youngest & the common ancestors = second cousins

And so on.

“Removed” simply means that one of the cousins has more generations between himself and the common ancestor than does the other. In the chart below, Tom and Alex are first cousins once removed, since Alex is one more generation “removed” from their common ancestors John and Emma.

Simple, oui? Hahahaha … I still have to sketch a little chart in order to figure out distant relationships. Alternatively, I could just enter the family into my family tree software and let it calculate the relationships. But what fun would that be?

See you on down the road. I’ve got a load of Rankins on my mind …