Triangulation - Try Again!

+2 votes

Last week I did an autosomal DNA confirmation to my second great grandparents Isaac Sidwell Cherry and Margerette Ellen Almon.  

This week I have found two distant cousins, 

1.  Joshua Robinett , (gedmatch YU8030481) 4th Cousin

2.  Lance Weast, (gedmatch PS7470617) 5th Cousin

They both have a 13-14cm chunk of DNA at the same spot on Ch. 20 and gedcom records back to the Almons.

Here is the question.

Joshua and I meet at Jabez Almon, Margarette's (who I already have DNA confirmation for) father.  

Lance comes from Jabez' brother so the most recent common ancestor is his father Jacob Almon.  

In the Triangulation Help file it says "All three legs should meet at the seat, or if not, then no more than one generation below it. Having two of the legs meeting closer to each other (e.g. two first cousins and a fourth cousin) does not make a valid triangulation. The stool would just fall over."  

So if both Joshua and I meet one generation down at Jabez and Lance is at the father Jacob.  Is this valid?  And the file also says, 

Do you include the MRCA? 

  1. If there is a single MRCA — because the matches are half-cousins, i.e. descendants of half-siblings who share only a mother or only a father — each child-to-parent relationship back to and including the relationship to the MRCA can be marked as confirmed.
  2. If there is a common ancestral couple each child-to-parent relationship back to but not including the relationships to the ancestral couple can be marked as confirmed. The relationships to the common ancestral couple can be marked as confident.

So do we include Jacob and Rebekah or just mark them as confident?  Do we include Jabez and Sarah or just mark them as confident?

WikiTree profile: Jacob Almon
in The Tree House by Jonathan Wilson G2G6 Mach 1 (11.0k points)

1 Answer

+7 votes
Best answer
Yes, you meet the stool criterion. Your and your two distant cousin’s situation is exactly what is meant by some legs meeting 1 generation below. The extra third cousin match you did last week is just icing (assuming that match also shares the chromosome 20 segment).

Per your other question — people aren’t confirmed, relationships are. If Jabez and Jacob were full siblings, you can confirm each relationship in your line back to Jabez, but not the connection from Jabez to Jacob since the segment could have come to Jabez from his mother.
by Barry Smith G2G6 Pilot (223k points)
selected by Jonathan Wilson
Barry, I just can't quite follow this.  Are Jabez and Jacob siblings, or father and son?
Father and son
And so if the segment came to Jabez from his mother, it would also have come to his (apparently unnamed) brother from the mother too, right?

P.S. I'm not trying to nitpick, I'm just trying to clarify.
Yes, absent evidence of some strange familial information (such has Jacob and his wife being close relatives).
So I am back to my second question.  

Jabez and John (brothers) passed their dna down to me, Josh and Lance,

Do I add their father Jacob and his wife Rebekkah as DNA confirmed?
My answer remains the same. I would not confirm the link from Jabez to either parent because you don’t know which parent gave him the segment.

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