Mystery match

[Family]

Hi, all!

My closest match was estimated as 2nd - 3rd cousin, with 220 shared cM, but, even though paper-wise my tree is pretty well researched, I couldn't determine the link. Subsequently I had both a maternal and paternal cousin tested, but disappointingly neither were a match to the 2nd/3rd cousin match. I understand how that happens, but I'm at a loss at to how to figure out how the 2nd/3rd cousin ties. And I can't really think of any more family members to test - small family. I've used the gedmatch.com resources as well as dnagedcom.com, but still haven't found any thing material.

Any thoughts for mysteries like this?

Thanks!

[MMaddi]

How deep is the tree of the 2nd-3rd cousin? If the match has only documented his/her ancestry to great-grandparents or less, the common ancestor may be just 1 or 2 generations further back. Also, with as close a match as 2nd-3rd cousin and a fairly deep documented tree on your part, there might be an NPE involved, either in your tree or that of the 2nd-3rd cousin.

Without a deep enough documented tree for the match, you'll have to concentrate on looking for common ancestral locations in the mid 1800s or so. That would probably put both of you back to the time that your great-grandparents or gg-grandparents were alive and having children. If you can find a common location in that period, especially the same town or rural area, that would help to narrow down in which line the common ancestor may be found.

[Family]

Hi, MMaddi!

Thanks for your response! I see that you're replying to both questions that I have on the forum right now - the other question is about the wide discrepancy in the shared cM with my two female cousins. Thank you!

For my mystery 2nd/3rd cousin, I have my line traced back, on paper, to my great-great grandparents for all lines. I have the mystery cousin's lineage back to great-grandparents for all lines. For the 16 g-g-grandparents, I'm missing 4.

I didn't realize until now that you had responded to my other 1st cousin question, as well, so this will be a repeat of what I just put in that post, but for my mystery male cousin when I click the arrow underneath his name, it shows "Y: R-M269 | mt: K1a3a1" Does that give me any useful
information?

Pretty much the sole reason I had my two 1st cousins - one paternal and the other maternal - tested, was to determine if the mystery 2nd/3rd cousin was tied to my maternal or paternal lines. But, to my disappointment, neither 1st cousin is a match to my mystery 2nd/3rd cousin. Would that be a reason to suspect an NPE, or should I reasonably expect that one of the first cousins would be a match to someone that shows up as a 2nd/3rd cousin to me?

Regarding locale, both my family and that of the mystery 2nd/3rd cousin, are firmly rooted in the same area - WV/OH border counties for both the maternal and paternal lines, so I don't have much to go on there.

Thanks so much!!!

[Family]

Hi!

MMaddi - I used your suggestion regarding my 1st cousin question, and used it for the mystery 2nd/3rd cousin - I downloaded the data from the FTDNA chromosome browser, and then deleted the segments under 5 cM. The result was 187 shared cM on 16 segments.

Thanks, again!

[MMaddi]

For my mystery 2nd/3rd cousin, I have my line traced back, on paper, to my great-great grandparents for all lines. I have the mystery cousin's lineage back to great-grandparents for all lines. For the 16 g-g-grandparents, I'm missing 4.

So, either the common ancestors for you and him are one of the two gg-grandparent couples of his that you don't know or there's an NPE involved. There's always the possibility that the actual relationship is more distant than what FTDNA has estimated, but when you get to the closer relationships, such as 2nd cousin, they're generally accurate, certainly more accurate than more distant cousin relationships.

I didn't realize until now that you had responded to my other 1st cousin question, as well, so this will be a repeat of what I just put in that post, but for my mystery male cousin when I click the arrow underneath his name, it shows "Y: R-M269 | mt: K1a3a1" Does that give me any useful
information?

Offhand, I don't think the haplogroup information will be of much use in figuring out the mystery match. Remember that the yDNA and mtDNA haplogroups only tell you about the strict paternal and maternal lines. At the level of gg-grandparents, there are 16 ancestors, with one being a strict paternal line ancestor and another being a strict maternal line ancestor. That means there are 14 ancestors in that generation who may have entirely different haplogroups than your strict paternal and maternal line ancestors in that generation. And R-M269 is the most common haplogroup among men with European ancestry. So, knowing that about your match doesn't really have much significance.

Pretty much the sole reason I had my two 1st cousins - one paternal and the other maternal - tested, was to determine if the mystery 2nd/3rd cousin was tied to my maternal or paternal lines. But, to my disappointment, neither 1st cousin is a match to my mystery 2nd/3rd cousin. Would that be a reason to suspect an NPE, or should I reasonably expect that one of the first cousins would be a match to someone that shows up as a 2nd/3rd cousin to me?

You share a set of grandparents with 1st cousins. By testing a 1st cousin from your paternal and maternal sides, that covers all your grandparents. It seems on the surface that someone as close as a 1st cousin would also match someone who's your 2nd cousin, since the 2nd cousin would share the parents of one of your grandparents with you, the same grandparent you share with one of the 1st cousins who tested.

However, there seems to be some question whether one of your cousins is actually a full first cousin, because of the low shared cM for the relationship. So, if that 1st cousin is not actually a full 1st cousin, that could mean that the mystery 2nd/3rd cousin match is from the side that the low shared cM 1st cousin is from - I forgot if that's paternal or maternal. In that case, the relationship between that mystery 2nd/3rd cousin and the low shared cM 1st cousin is a bit more distant. Then perhaps it's distant enough that the mystery 2nd/3rd cousin doesn't share enough DNA with the low shared cM 1st cousin to show up as a match or is showing up as a more distant estimated match.

I think that makes sense.

[MMaddi]

Hi!

MMaddi - I used your suggestion regarding my 1st cousin question, and used it for the mystery 2nd/3rd cousin - I downloaded the data from the FTDNA chromosome browser, and then deleted the segments under 5 cM. The result was 187 shared cM on 16 segments.

Thanks, again!

The number of segments looks like a 2nd cousin, which are usually double digit. In my experience, double digit shared segments would usually indicate 2nd cousin; 5-9 shared segments would usually indicate 2nd cousin, once removed; and 2-4 shared segments usually indicate 3rd cousins.

However, the total shared cM of 187 is low for a 2nd cousin. It sounds like many of the 16 segments are not that large. How many of the 16 segments are over 15 cM and how many are under 10 cM?

Also, is the ancestry involved for you and the mystery match from an endogamous community of some sort - Ashkenazi, Colonial American or French Canadian? These communities had long periods of cousin marriage in a small population group. So, they pass around the same segments that have been preserved longer than for non-endogamous communities. That's why matches with this type of ancestry may be estimated as closer cousins than they actually are.

If you and the mystery match both have Colonial American ancestry, then I think the relationship may be more distant than 2nd-3rd cousin.

[Family]

Hi!

Thanks for your reply!

Given that I have the mystery 2nd/3rd cousin, and I have a 1st cousin (maternal cousin - daughter of my mother's sister) who doesn't come in as a particularly strong 1st cousin match, the most likely scenario that comes to my mind is that the father of my mother is not the same as the father of my 1st cousin's mother. And that the mystery 2nd/3rd cousin is related to my mother's (unknown) father.

Would that be your best guess? Or am I leaping to conclusions?

Thanks!!!

[MMaddi]

Hi!

Thanks for your reply!

Given that I have the mystery 2nd/3rd cousin, and I have a 1st cousin (maternal cousin - daughter of my mother's sister) who doesn't come in as a particularly strong 1st cousin match, the most likely scenario that comes to my mind is that the father of my mother is not the same as the father of my 1st cousin's mother. And that the mystery 2nd/3rd cousin is related to my mother's (unknown) father.

Would that be your best guess? Or am I leaping to conclusions?

Thanks!!!

What you've suggested is certainly a plausible explanation that fits the numbers. The other possibility, which I suggested in my previous post, is that there's endogamy involved in the ancestry of you and the mystery 2nd/3rd cousin that's causing the estimated relationship to be closer than it actually is.

[Family]

Hi!

Thanks for your input!

The mystery 2nd/3rd cousin shares 6 segments between 5 and 10 cM, 6 segments between 10 and 15, and 4 segments over 15 cM.

I'm not sure, but I think my ancestry might qualify as Colonial American. Most recent arrivals that I know of are two of my g-g-g grandparents - one b. 1759 England and one b. 1742 Ireland.

The mystery cousin has more recent arrivals - a great-grandparent b. 1842 Ireland, and 4 g-g-grandparents from Ireland. But still some pretty deep roots, and in the same area as my ancestors - southeast OH and northern WV.

Thanks much for any thoughts you have!

[MMaddi]

Hi!

Thanks for your input!

The mystery 2nd/3rd cousin shares 6 segments between 5 and 10 cM, 6 segments between 10 and 15, and 4 segments over 15 cM.

For comparison sake, here are the numbers for sharing that my sister and I have with a known 2nd cousin at 23andMe:

2nd cousin and I share 472 cM in 14 segments, with 2 between 5 and 10 cM, 1 between 10 and 15 cM, 2 between 15 and 20 cM and 9 more 24.6 cM or higher.

2nd cousin and my sister share 297 cM in 13 segments, with 3 between 5 and 10 cM, 3 between 10 and 15 cM, 2 between 15 and 20 cM and 5 of 22.9 cM or higher.

The amount I share with the 2nd cousin is at the high end of the sharing range for 2nd cousins, putting it slightly above the average sharing (440 cM) of 1st cousins, once removed. The chart of shared cM that I linked to in your other thread puts the average shared cM for 2nd cousins at 246 and my sister shares 297 cM with the 2nd cousin. So, it's probably better to compare your sharing with the mystery match with my sister's sharing with our 2nd cousin.

Based on that comparison, it doesn't seem like a 2nd cousin relationship to me, although the number of segments are about right for a 2nd cousin relationship.

[Family]

Hi!

Thanks so much for sharing the numbers that you and your sister share with a 2nd cousin. It helps to have a real example of what the numbers look like and how they vary from you to your sister. I appreciate you taking the time to share your knowledge with me!

[mattn]

Your match appears likely to be a 2nd cousin based on amount shared and number of segments. If you tested both a maternal and paternal first cousin and neither match this person then you are most likely looking at an NPE somewhere. It sounds like from your other thread that it would be there with your maternal side (it could be very possible that your mom and her sister only shared one parent).

[MMaddi]

Your match appears likely to be a 2nd cousin based on amount shared and number of segments. If you tested both a maternal and paternal first cousin and neither match this person then you are most likely looking at an NPE somewhere. It sounds like from your other thread that it would be there with your maternal side (it could be very possible that your mom and her sister only shared one parent).

You may be right about the mystery match being a 2nd cousin, but the amount shared seems low to me. I'm thinking that the mystery match may be a 2nd cousin, once removed or even a high sharing 3rd cousin. That's based on the ISOGG chart at http://www.isogg.org/wiki/Autosomal_..._of_shared_DNA.

See my posts earlier in this thread - http://forums.familytreedna.com/show...71&postcount=6 and http://forums.familytreedna.com/show...5&postcount=10 - to see my reasoning on this. Do you think the mystery match is more likely to be a 2nd cousin or 2nd cousin, once removed?

[mattn]

You may be right about the mystery match being a 2nd cousin, but the amount shared seems low to me. I'm thinking that the mystery match may be a 2nd cousin, once removed or even a high sharing 3rd cousin. That's based on the ISOGG chart at http://www.isogg.org/wiki/Autosomal_..._of_shared_DNA.

See my posts earlier in this thread - http://forums.familytreedna.com/show...71&postcount=6 and http://forums.familytreedna.com/show...5&postcount=10 - to see my reasoning on this. Do you think the mystery match is more likely to be a 2nd cousin or 2nd cousin, once removed?

I was basing being a solid 2nd cousin by this chart:

http://www.isogg.org/wiki/Identical_by_descent

(see: "Ranges of total centiMorgans of IBD segments based on family relationship").


You're right MMaddi I could be mistaken and it could be 2nd cousins once removed too as a possibility but the number of segments seemed to point more to 2nd cousin. The main thing I was trying to convey is that there seems to be a possibility of an NPE here based on the very low first cousin match coupled by a close match where the paper trees seemingly don't overlap.

[MMaddi]

I was basing being a solid 2nd cousin by this chart:

http://www.isogg.org/wiki/Identical_by_descent

(see: "Ranges of total centiMorgans of IBD segments based on family relationship").


You're right MMaddi I could be mistaken and it could be 2nd cousins once removed too as a possibility but the number of segments seemed to point more to 2nd cousin. The main thing I was trying to convey is that there seems to be a possibility of an NPE here based on the very low first cousin match coupled by a close match where the paper trees seemingly don't overlap.

Yes, I see your point about the numbers of segments shared. That would be outside the norm for 2nd cousins, once removed.

However, I've brought up the possibility that ancestry from an endogamous community, maybe Colonial American, may be causing the relationship to seem closer than it actually is. Although, based on the OP's response about his and the mystery match's ancestry, the potential for significant Colonial American ancestry affecting the sharing doesn't seem to be that high. See his post about that at http://forums.familytreedna.com/show...74&postcount=9.