DNA Triangulation

By Kitty Cooper

blog. kittycooper. com

ISOGG wiki entry for Triangulation


  • When three people all match each other at the same autosomal DNA location we call it Triangulation.
  • From ISOGG: "If you have at least three people with a common ancestor matching on the same segment then you can infer that the segment came from that ancestor. "
  • Inversely, if three people all match each other on the same segment then you can infer they have a common ancestor.

Blaine Bettinger's new DNA relatedness chart, from his site http://www.thegeneticgenealogist.com/








There was a thin paper trail suggesting Kristine was our cousin via George Wald, possible son of Charlie Wold ... so I got a number of WOLD cousins to test their DNA to see if that was so

KRISTINE v my cousins

Kristine compared to Mike and John on chromosome 11


Chr 11

Kristine compared to John, George and Henry

John versus 2nd cousins
George (PG) and Henry

Chr 14


Kristine compared to Mike and Katy


Chr 16

More recently I found a grand daughter of Charley and got her, MM, to test too

The total number of cMs seemed low until I realized that she was from a different wife of Charley so a HALF 1C2R

Only one of the five segments MM shares with Kristine are in the same location as the other cousins, the one on chr 11, does it triangulate?

My fourth grandparents lived on VE farm in Etne , Hordaland and I have this triangulation group for the cousins descended from them
I told Shelley she triangulated into that group very small so probably too far back. She replied my great grandmother was Anna VE ... so I quickly figured out that we are 5th cousins once removed
Investigating a new match with a surname I recognized, Brekke ...
LuAnn matches dad and my brother but not me or either 2nd cousin

Another way to triangulate is to use other known relatives. Sometimes my brother and I got opposite segments from our Dad

These are my dad's matches: Everyone marked M for maternal matches my brother Ship, but the P for paternal matches me

Comparing LuAnn to the matches each side of her in the spreadsheet as well as to us we see this
Since LuAnn matches Ship and Lester she must be maternal


Gunnar versus my Dad

Gunnar versus my Dad

Gunnar versus my brother

Top matches Dad has in common with Gunnar

Gunnar versus Kitty, no match on 2, match on 20

Dad's Matrix Matches

How to get a Chromosome Browser Results (CBR) file

DMT output as a CSV

Automated Triangulation Tool at GEDmatch.com

GEDmatch triangulation sorted by chromosome location

Gedmatch Triangulation for Dad sorted by Match Name

Cousin Katy

Gedmatch Triangulation for Dad cut and pasted to a spreadsheet then sorted by chromosome and start

When you look at your shared matches at MyHeritage, this icon to the right of the match tells you there is at least one segment that triangulates
When you click on that triangulation icon you get a page like this where the matching segments are shown with the triangulating ones outlined


DNA Triangulation -2018

By Kitty Cooper

DNA Triangulation -2018

How to use triangulation to confirm DNA relatives

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