Wednesday, May 5, 2021

Dear Randy - How Many DNA Matches From Your 3rd Great-Grandparents Do You Have by ThruLines in AncestryDNA?

A society colleague asked this question recently in a Zoom meeting, and I responded "428" because I recently did the "Common Ancestor" analysis using a Google spreadsheet (see Downloading My AncestryDNA Match List With Google Sheets, although it's been improved).  I note that 428 is 1.2% of my AncestryDNA match total of 36,566 as of today.  

1)  However, I don't know, offhand, how many of my ThruLines are from each generation of my ancestors.  So I went into my ThruLines to count them by my 16 3rd great-grandparents couples:

My father's 3rd great-grandparents:

* Benjamin Seaver and Abigail Gates: 2
* Alpheus Smith and Elizabeth Dill - 0
* Zachariah Hildreth and Hannah Sawtell - 13
* Lambert Brigham and Sophia Buck - 1
* John Richman and Ann Marshman - 21
* John Rich and Rebecca Hill - 16
* Jonathan White and Miranda Wade - 13
* Jonathan Oatley and Nancy Champlin - 11

My mother's 3rd great-grandparents:

* Henry Carringer and Sarah Feather - 6
* Daniel Spangler and Elizabeth King - 20
* Samuel Vaux and Mary Ann Underhill - 2
* ????? Lanfear and ????? ????? - 0
* John Auble and Anna Row - 7
* William Knapp and Sarah Cutter - 4
* Abraham Kemp and Sarah Fletcher - 19
* Alexander Sovereen and Eliza Putman - 4

For this "counting" I did not count matches that were already counted - like myself and my two first cousins who descend from my paternal grandparents (who were counted in the Seaver/Gates number). 

2)  So the total of "nominal" 4th cousins from my 3rd great-grandparents is 77 from my father's side and 62 from my mother's side, for a total of 149.  As far as I can tell, all 149 of these ThruLines are correct, and almost all of them are in my RootsMagic family tree.

The other 279 ThruLines come from more distant common ancestors, so I will do the same for my 4th cousins in other blog post.

3)  Why do I have so few ThruLines for some of my 3rd great-grandparents?  The simple answer is that I have found few 4th cousins or closer for many of these 3rd great-grandparent couples - especially the Seaver/Gates, Smith/Dill, Brigham/Buck, Vaux/Underhill, Lanfear/?????, Knapp/Cutter and Sovereen/Putman couples.  Some of those couples had only 2 or 3 children that married, and some fraction of each line dies out with no children born to a couple.  Another reason is that these 3rd great-grandparents of mine were born in the 1780-1820 time window, and many DNA matches don't have an Ancestry Member Tree with ancestors back that far in time.

The 4th great-grandparent list may be a bit more numerous because families were larger in the 18th century and there are many more descendants for some of them.  I will do them in a separate blog post, and may do the 5th great-grandparents as well.

5)  I would be interested to know how many ThruLines other researchers have from the 3rd, 4th and 5th great-grandparents.  If you put them in Comments to this post, I will see them.


Disclosure: I have a complimentary all-access subscription from, for which I am thankful. has provided material considerations for travel expenses to meetings, and has hosted events and meals that I have attended in Salt Lake City, in past years.

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