Creating a Surname Table With Tree Collapse (aka kissing cousins)

SYNTHPOPALOOZA asked in our post Our Surname Tables for DNA Research

What do you do in the case of first cousins marrying each other? This happens three times in my tree, and in one case (my father's father's line) both my 2nd great-grandparents have the same last name, Hurst. They share the same grandparents. How do you chart that?

Great question. I have some suggestions but before we jump into answering that question, if you want step-by-step instructions on how to create a surname table, this video should help.




Back to the actual question of charting when cousins marry each other. What you are describing is tree collapse. BOY, oh Boy, will your DNA become very confusing. Your cousin matches might suggest someone is more closely related to you than they actually are when you map our your family tree using documents. The more occurrences of tree collapse you encounter, the more confusing your research becomes, as you well know. I do not envy your situation. However, here's how you can demonstrate tree collapse with a surname table.


Tree collapse on different grandparent lines.
(The right column is not accurate, so please don't use this table for proof)

This first example shows tree collapse when two sisters marry individuals that will eventually have a common great-great-grandchild. It's not cousins, but it is problematic.

Notice how I first built the surname table as I would for any family without tree collapse. The only difference is I added numbers beside the surnames. For the two sisters, I used (1 + letter). This indicates that they are of the same generation and that they are siblings. Otherwise, if I was using a numeral alone (2), (3), or (4), then I am indicating the same person.

Do not cite this table as fact, it was modified for instructional purposes.

This surname table has tree collapse along the same line because a brother and sister marry each other. The surname Zumstein in the 2nd GGP generation, based on its placement in the chart, represents the mother of the Comfort in 1st GP position.

The (1*) is used to indicate that this female is a sibling to the male who had a child with the woman with the last name Snyder. To ensure clarity, I added a footnote to the table. This will help if your tree collapse occurs in multiple locations on your tree.

From this point forward, I continue to create the surname table as I would any other family. I add parenthetical numbers, (2), (3), (4), for those individual who are the same person in the tree. In so doing, I am suggestion their male partners are also the same.

If you have more tree collapse, you'll use increasing larger numbers or come up with a creative number system (i.e., Z1 ~ for the start of the Zumstein tree collapse, C1 ~ for start of the Comfort tree collapse).
The numbers help me see the pattern of tree collapse. Are you able to see the reduced tree in the 4thGGP generation for the Zumstein line, can't you?

I hope this helps SYNTHPOPALOOZA with her situation. If you have questions about anything we post here on Family History Fanatics, drop us a comment below the specific post, and we'll be happy to respond your comments or create additional articles when the answers are longer than a quick reply can answer.

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