+3 votes

i HAVE triangulation on CM 10 with a 4th and 5th cousin.

we share 15.3 cm on chm 10 would like help doing confirmation cole-1422

the shared dna has to be Mark Cole-1422 as two of us descend from Sussanah and the other from her sister Hannah Jemima Cole.

Thank you, Sherry

WikiTree profile: Sherry Holston
in Genealogy Help by Sherry Holston G2G6 Mach 1 (19.7k points)
You have a triangulation, you know the common ancestor, you have the three-legged stool... all is in order, so what is the question? How to write the citation? Which relationships to mark confirmed?
First time I did a non 2nd or 3rd cousin one since Brian and I share Suzannah Cole we should be able to confirm her and Mark Cole. Kyle should be able to confirm Susannas sister Hannah and Mark? Same citation as 3rd cousin but mention triangulation? Is it a problem that one is a 4th cousin 1x removed and the other is a 5th cousin?

Thank you,


Hi, Sherry. I hate to be the bearer of bad tidings, but I thought I'd take a quick look at the triangulation on your profile to see if I could add anything. Unfortunately, it isn't a triangulation per WikiTree guidelines. On GEDmatch, if you compare the two kits that begin with M64 and A38, you'll see that their small shared segment on Chromosome 10 ends before the start of the segment you share with either of them. You don't all three share any in-common segments.

It would be clearer if we could show the actual data, but I believe that's now limited for privacy's sake. But maybe this might help. The Chr 10 segment that M64 and A38 share shows as ending at locus xx6,383,363. Your Chr 10 segment match with M64 starts at xx6,569, 185,840 base pairs separate the two segments. The segment you share with A38 has even more separation, starting at xx8,608,985. The loci hold true whether or not the "Prevent Hard Breaks" comparison option is enabled. So there's no segment overlap all three of you share mutually. That make any sense?

Comparing Kit GR4297284 (*Stardust) [FTDNA] and A386617 (*BF4) [Migration - F2 - A]

Chr B37 Start Pos'n B37 End Pos'n Centimorgans (cM) SNPs


10 128,608,215 133,742,677 15.5 1,931 84.00

Comparing Kit GR4297284 (*Stardust) [FTDNA] and M648925 (Kyle Stewart) [Mig

Chr B37 Start Pos'n B37 End Pos'n Centimorgans (cM) SNPs
10 126,554,570 131,726,740 15.4 951 126.00

I guess I don't need to worry about the privacy aspect.  laugh

The trick with triangulation, though, is that all (at least) three people must share at least one identical segment. That means, in this case, you also have to compare kit M648925 with kit A386617...not just you to each of them. What those two share is an 8cM segment on Chr 10 from 122,124,258 to 126,383,363. That segment doesn't overlap with what you share with either of them.

Edison is correct.  Please post this match or the 3rd leg so we can see the results and if in fact they match each other on Chrom 10 overlapping between 128,608,215 - 131,726,740 and you will see they just miss overlapping!

Close but no cigar on this match.  You may still match, but need another candidate.

Comparing Kit M648925 (Kyle Stewart) [Migration - V4 - M] and Kit A386617 (*BFlynt74) [Migration - F2 - A]

Chr B37 Start Pos'n B37 End Pos'n Centimorgans (cM) SNPs
5 171,049,530 178,827,859 18.9 1,139
9 85,895,419 93,658,206 13 1,006
10 122,124,258 126,383,363 8 728

2 Answers

+4 votes
Best answer
4C1R vs 5C is not a problem. You just need to all have separate lines from the most recent common ancestor Mark, or else to of you can have lines meeting one generation below him, i.e., you and Brian.

You cannot confirm the relationship to Mark, because his wife Hannah could have been the one who supplied your shared DNA. But all relationships on the line back to Susannah could be confirmed.  Example citations are on the Triangulation Help page:

You mention "Hannah Jemima." To be clear, that is Susannah's sister? I'm not seeing "Jemima" on her sister's profile. But only a few people born in the 1700s had a middle name, so that could be incorrect.
by Barry Smith G2G6 Pilot (244k points)
edited by Barry Smith
Since the sisters are proven would not both Mark and his wife Hannah Spell be proven?

Thank you,

If the are full sisters, then no. The segment of DNA you and your matches share may have been in Mark. Or it may have been in Hannah. Both daughters only got it from one of these parents, and then they passed all the way down to you and your matches. The other parent did not contribute that segment. You can only mark as confirmed the connection to the one parent who did supply the DNA segment. But since you don't know if that was Mark or Hannah, you cannot mark either as confirmed.

If Susannah and Hannah were half-sisters, say with only the father Mark in common, then you could be sure that Mark was the source of that DNA segment. But with full siblings, you just don't know which parent to confirm, so you can't confirm either.

Sorry, Edison is right smiley

Or build a wiki tree profile for Kyle and invite Kyle to Wikitree
Thank you! Kyle though is on Wiki Tree she has a wiki Id but is living.

GEDmatch® Q-Matching One-to-One Comparison - V1.0

Software Version Sep 28 2020 21:29:42
Comparing Kit M648925 (Kyle Stewart) [Migration - V4 - M] and A386617 (*BFlynt74) [Migration - F2 - A]Precision: 30.0cM threshold: 7.0Maximum cM: No LimitGap threshold: 2.0 cM'sAll SNPs used.


Chr B37 Start Pos'n B37 End Pos'n Centimorgans (cM) SNPs
10 122,113,893 126,383,857 8.1 728 91.00
There is not room to put it all but it looks like they match each other at 8 and me at 15.3 each and that is in one to one Qmatch. Why is that not a triangulation? i have about 5 people who match to me on that line and come up in most recent common ancestor. Some have higher matches but the problem is finding a Chromosome position sequence we all match on. Thank you for your assistance but I am just not seeing why it is not a good match.
Because it is the two numbers with all the commas that matter, not the 8.1 and 15.3. These segments very well could be all from the same ancestor. But you don’t all match on the exact same chunk of chromosome 10, so it’s not triangulation.
+4 votes

It would seem that the directions for triangulation are not clear enough. It currently states that "Three or more cousins need to all match each other on a single segment of DNA that is at least 7cM long." Providing definitions for segments and centimorgans (cMs) would help. 

Segments are defined by their start/end positions on the single shared chromosome. If the shared segment is identical for all matches, the amount of shared cMs will be known. If the shared segment is not identical for all matches, instructions on how to determine the amount of shared cMs from the start/end positions of the shared segment should be included

John Kingman

by John Kingman G2G6 Mach 5 (50.9k points)

Also if hard breaks needs to be marked in triangulaion. I just ran through triangulaion again but did not mark the hard breaks button and it shows triangulation with 4 people and me on the same sequence.

130,499,623 133,466,045 9.8
126,743,096 133,355,589 19.2
126,743,096 131,598,860 14.4
130,499,623 133,355,589 9.5
10 M648925 126,569,203 131,711,365 15.3
10 M648925 126,743,096 131,598,860 14.4
126,569,203 131,711,365 15.3

Also if hard breaks needs to be marked in triangulaion. I just ran through triangulaion again but did not mark the hard breaks button and it shows triangulation with 4 people and me on the same sequence.

Hi again! I think you'll find that A589040 and M648925 share no meaningful DNA with each other. So one of them cannot be a part of that particular triangulation group. I suspect the one you'd want to eliminate would be A589040 because that leaves the rest of the four of you sharing a segment that begins at 126,739,338 and ends at 131,600,411, which would be approximately 14cM under GRCh37 (or hg19, what GEDmatch calls B37).

And of course A386617 isn't listed in that table even though it was one of three kits used in the original triangulation that started the topic. I did a quick GEDmatch Segment Triangulation report for A386617 (using default settings and on Chr 10 only), and your kit number, Sherry, doesn't appear on the report...which only means that you and A386617 don't have a third kit at GEDmatch that matches up with the two of you; doesn't mean you aren't the cousins the paper-trail says you are.
Hi Edison, I believe you are mistaken the kit you put in first is compared to the other kits. If you do not triangulate, you get nothing. If you do triangulate it compares the kits which match you to each other. I the last triangulation I sent only showed a few and K Stewart And MFlynt were on it. I ran again with BFlynt as well and they do triangulate.

GEDmatch Triangulation of Selected Kits-- V0.3)
Triangulation with Kit GR4297284 - *Stardust.
All kits shown in columns Kit1 and Kit2 are taken from the selected kit matches to GR4297284.
This is an indication of common ancestry.
Segments shown are larger than 7.0 cM and between 200 and 400 SNPs.
Triangulated results sorted by Chromosome, Start Position
B37 End cM
131,711,365 15
131,598,860 14
133,355,589 19
133,729,749 16
133,355,589 14
133,355,589 9.5
133,466,045 9.8
133,466,045 9.2

Sherry, you're using a visualization option following a One-to-Many search. That will not give you valid results for this purpose because it doesn't perform complete segment triangulation. You're not comparing everyone in the hypothetical triangulation group to everyone else based upon cross-matched segments.

Go to either the regular or Tier 1 One-to-One matching tools and compare A589040 and M648925:

Comparing Kit A589040 (____) [Migration - F2 - A] and Kit M648925 (____) [Migration - V4 - M]

Segment threshold size will be adjusted dynamically between 200 and 400 SNPs
Minimum segment cM to be included in total = 7.0 cM

No shared DNA segments found

Those two kits have no meaningful DNA in common. You would need to drop down to 4cM or below to find any tiny segments that they might share, and none of those are on Chr 10.

If you want a real-world example of why tiny segments can't be used, try running a Q Matching One-to-One of your kit against mine, QJ297469C1, with the threshold lowered to 3cM. I'm sure we can agree that our family trees give no indication at all that we should share 65.4 cM across 18 segments. These are all either false segments, testing artifacts, or are IBS-only as a result of very deep population-level ancestry that can't be applied genealogically.

If you want to use the GEDmatch segment triangulation tool, it's under Tier 1, "Triangulation." You enter only one kit number, so use yours. Choose only Chromosome 10, and select "Cross-match triangulated segments with others within chromosome." You can leave everything else at the default values.

Because the starting locus of all the matches we're talking about is near the telomere, at the end of the chromosome, the calculated triangulation group will be shown at the end of the first section.

I'm including only the kit numbers, not the names, but the individuals who are in TG10_8 Chr 10 are:

Triangulated Group Names:
 kit: A164431 Name: ____
 kit: A589040 Name: ____
 kit: HZ4084826 Name: ____
 kit: M012661 Name: ____
 kit: M814622 Name: ____
 kit: RL5365418 Name: ____
 kit: SY1898734 Name: ____

So not appearing in the triangulation group are M648925 and A386617. I personally never rely solely on the "GEDmatch Segment Triangulation" report without building a one-to-one matching matrix myself in order to better understand how everyone involved compares to everyone else.

Also, as popular genetic genealogist Jim Bartlett reinforces over and over, we shouldn't think of triangulating people, but segments. Sometimes you might want to subdivide a triangulation group further because, even though everyone in the TG might share a segment, it might only be only a small segment...since we have to look for the lowest common denominator. For example, if I match you from 10 to 200, and my cousin Whozzat matches me from 10 to 900, but matches you at 198 to 700, then our in-common, mutually-shared segment is only 198-200...because that's the only small bit we all share with each other.

I wanted to avoid adding this, but I feel it's sorta necessary now, all things considered. There is still no scientific, peer-reviewed research that indicates our method of triangulation of distant cousins for genealogy with our popular microarray tests has any validity. Intuitively, it would seem it should work for relatively close cousins, but there are several reasons it should not work for distant cousins. The simple biological mechanisms of meiosis and independent assortment greatly stack the odds against it functioning as many believe it least if we're talking about descendancy-identifiable data and not merely exonic or continental population-level SNPs.

For the very same reason that no two siblings have the same DNA (other than monozygotic twins)--even if the couple has 20 children--the odds of any three distant cousins sharing any measurable-via-microarray DNA quickly becomes astronomical. For example, when AncestryDNA still used DNA Circles and calculated down to 5cMs (they now use 8cM), their Help paper on the subject said:

Our research shows that the chances that three first cousins will all have the same matching segment (in this case one that is at least 5 cM long) is about 85 percent; three third cousins have only a 15 percent chance. And the chance that three fourth cousins will all share the same matching segment is practically zero.

The emphasis is mine. And, mind you, Ancestry was talking about the available data after they had scrubbed the matches using the BEAGLE and Timber algorithms. I've been hoping for quite some time to see solid research that would simulate the DNA inheritance conundrum triangulation of distant cousins presents, but I take Ancestry's stance actually to be on the optimistic end of the spectrum.

If we were to apply the same, simple probability calculation of three mutually independent events--like rolling three dice and having them all come up on the same number--and apply it to data like we see in an important paper that evaluated real data from 23andMe (Henn, et al. PLoS One, 2012), we'd see that the probability of three 5th cousins sharing a genealogically meaningful matching segment would be 0.003308; for 6th cousins it would be 0.000069. If we could effectively do simulations I have a feeling the results wouldn't be quite that low, but they would still be very in highly improbable any three 5th cousins or greater would share a meaningful matching segment. And it wouldn't matter if the individuals were absolutely correct in the family tree or not. The way our biology is engineered for genetic diversity simply shouldn't allow it to happen very often at all.

We have generally accepted guidelines here and elsewhere for autosomal triangulation of distant cousins, but for the purposes of your own research with a goal toward accuracy, this is just a parking-lot notation that nobody knows if it actually works, if it actually reveals any valid genealogical information.

Thank you! I did not realize that Triangulation reached through Multiple Kit Analysis was different than Triangulation for one kit. I still don"t understand why I get such different numbers even in 1 to 1.BF matched to me shows these segments

Chr B37 Start Pos'n B37 End Pos'n Centimorgans (cM) SNPs Q
10 128,608,215 133,742,677 15.5 1,931 84

The above was 1 to 1 Tier 1 but does not come up in triangulation Segments. When I match MF to BF 1to 1

Chr B37 Start Pos'n B37 End Pos'n Centimorgans (cM) SNPs Q
10 4,070,444 14,625,801 23.7 1,966 303
10 129,096,956 134,191,811 15.4 1,009 138
MF does come up in Segmet Triangulation and I am pretty Certain that LF who also comes up in triangulation MF and BF are all related.

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