Adding a great-grandfather that is only known to be one of four brothers

+4 votes
My paternal great-grandmother never married and never revealed who the father of my grandfather was.  Through family rumors, we had some clue.  Recently, I found a male descendant of the possible father's family who agreed to a DNA test.  We both took paternal DNA-111 tests.  It shows we have a genetic distance of 0.  First of all, is this considered sufficient to say that we have a common male ancestor within 3 or 4 generations?  Secondly, if that is the case, yet the ancestor could have been one of four brothers, is there any way to add this information into Wiki Tree?  If I can insert that "possible" ancestor, then I can definitely add his father and continue discovering ancestors on that line.

For more clarity, the lines are as follows:

myself => Jimmy Armstrong => Archie Armstrong => Haney Armstrong (she never married)

male Leak => his father => his grandfather => his great-grandfather(one of the four brothers) => Jeremiah Leak

Any advice is most appreciated.
WikiTree profile: Mark Armstrong
in Genealogy Help by Mark Armstrong G2G Rookie (280 points)
retagged by Mark Armstrong
Its my understanding that WikiTree follows your family tree, when it comes to DNA, the DNA doesn't establish it.  

This means that you can add the profiles for the people, with or without DNA.  I suggest including sources to show that each one lived, married, answered a census, or left another footprint, and/or died.  

I wouldn't necessarily add Mr. Leak as a biological father for Archie (forgive me if I didn't follow the relationships correctly) until you have confidence, but you could certainly note it in the biography for him and for his possible son.  Here is a tip on how to link in the biography:

As for the DNA-related question about genetic distance, if you tag DNA in your question, you may draw an expert into the discussion more quickly.
Thank you so much for the information.  I've added the DNA tag.

2 Answers

+3 votes
Best answer
Hi, Mark. Generally speaking, a genetic distance of zero at 111 STR markers means a 50% chance that two men share a common ancestor within two generations; a 90% chance within four generations; 95% within five; and 99% within six. You've got the correct line.

The "TiP" tool at Family Tree DNA will help narrow those probabilities a bit, but it's still all about probabilities. From your display of yDNA matches in your FTDNA dashboard, next to this match's name click the little "TiP" icon. When it displays, set the the option to display the results for each generation, not every four. TiP tries to take into account the variable average mutation rates of certain markers--and in some cases, mutation rates within specific haplogroups--to refine the odds. I believe they'll still show it's a done deal by or before six generations, but may refine things a bit for generations three to five.

From the info, since the MRCA would seem to be, at most, Jeremiah Leak's father, this puts things within the generational range for autosomal DNA detection.

With the current sale at FTDNA, a $59 Family Finder test on your new cousin's part should help nail down the relationship; you can transfer your Ancestry raw data to FTDNA and pay a $19 fee to "unlock" it for matching purposes. The results would clarify one of three possibilities: you and he share around 215cM, are 2nd cousins, and both descend from the same son of Jeremiah; you and he share around 55cM, are 3rd cousins, and descend from two different sons of Jeremiah; you and he share around 15cM, are 4th cousins, placing the MRCA at the generation of Jeremiah's father, meaning that it's likely one of Jeremiah's brothers is actually the 2g-grandfather. I sincerely doubt the MRCA is any farther back than Jeremiah's father.

The DNA can't tell you precisely who Haney was interested in, but you've already narrowed it down to the neighborhood and another step with autosomal testing should rule out most of the houses on the block, letting you focus your paper-trail research on very specific targets.

And I agree with Laurie: you can/should add the Leak families to WikiTree, or expand the details/source citations if they're already present. Gives you a place to organize your research; let's others in the same related lines find it; and your new cousin may want to join and help with the documentation. I personally wouldn't flag any of the four brothers as even "uncertain" as your great-grandfather at this point; you have strong evidence that you have the correct family, but it sounds like you're still a bit too far away from forming a workable hypothesis about the specific individual.

Good luck! You're close to big breakthrough!
by Edison Williams G2G6 Pilot (454k points)
selected by Douglas Beezley
I was pondering over my answer and posted before I saw yours. I'd say yours is stronger than mine so I'm picking it as "Best Answer".
+2 votes
I would consider 111 markers at GD0 to be quite strong. I work mostly with 67 markers (98 YDNA tests in the Beasley Project) and I would consider 67 markers at GD3 to be reasonable for common ancestors back to the mid 18th century.

I have several instances where the earliest confirmed ancestor and his sons are well documented, but there is some doubt about which grandson belongs to which son. I haven't had a chance to get some of these on, but what I would do is to look at whatever evidence I could find, even if weak, and grab one of them as the "hypothetical" father. Then I'd mark it with the {{Uncertain Family}} template and provide the explanation in the Bio. For the possible fathers that I didn't choose, I'd note "see also"
by Douglas Beezley G2G6 Mach 3 (36.9k points)

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