Double First Cousins
Overheard in GenForum, December 28, 2000
Q: Patrick married Elizabeth. Patrick's sister Johanna married Elizabeth's brother, John. Their children were double first cousins. What does that do to the generations that follow? Does that change their level of kinship? It is certainly a stronger blood tie than if the cousins weren't descended from the same two families. -- Debbie
A: Kinship is often one of the most confusing aspects of our genealogical research. We are often trying to figure out how we are related to a fellow researchers. We are sure they are a cousin, but determining that relationship is sometimes difficult to pin down exactly, especially if you are new to researching your family tree.
Most of the time questions deal the word "removed" and what is a second cousin. However, there are a number of other relationships including double first cousins and others.
Kinship degrees can be confusing.
A double cousinship occurs only when a set of siblings marries another set of siblings and both have children. This could be two sisters marrying two brothers. In your case, this is a brother and sister marrying a sister and brother.
Double cousins actually share the same gene pool as siblings. They share all four of the same grandparents. Most cousins share only one set of grandparents.
Cross and Parallel Cousins
First cousins can also be cross cousins. Cross cousins are those cousins who descend from a brother and sister. In your case, it was two sets of siblings, but they were still cross cousins.
There is another type of cousinship that is possible with first cousins. When the siblings are the same, as in two brothers or two sisters, the offspring, in addition to being first cousins, are also known as parallel cousins.
Affecting Further Generations
While double first cousins are double because they share both sets of grandparents, that is generally where such special references end. As you get to second cousins on down, the tree for proving this shows descent from a single individual. While these individuals would obviously be second cousins on many lines, that is where the special circumstance ends.
Rhonda R. McClure is a professional genealogist specializing in celebrity trees and computerized genealogy. She has been involved in online genealogy for fifteen years. She is an award-winning author of several genealogy how-to books, including The Complete Idiot's Guide to Online Genealogy, The Genealogist's Computer Companion, and Finding Your Famous and Infamous Ancestors. She may be contacted at firstname.lastname@example.org.
See more advice from Rhonda in her columns Expert Tips, Tigs and Trees, and Overheard in the Message Boards.