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Old 26-09-19, 03:05
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marquette marquette is offline
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Default DNA Puzzle

My second daughter has now had her DNA analysed on Ancestry.

We are getting quite a group now - 2 of my daughters (F and B) and my niece (R), my dad (L), my first cousin (P). My husband's two sisters (LM and BT) are also there.

On GEDmatch, we have me and my husband, his sisters and an aunt, and my girls.

The little puzzle is both my girls (F and B) have a small 8cM match with a man (MR). Ancestry is suggesting common ancestors in two of their 5xg grandparents who lived in Wokingham Berkshire, William Chaplin and Mary Trumplett.

But MR does not share any DNA with my Dad (L) or my cousin (P), or their cousin (R). Nor with any of the other 30 or so descendants of the family in Australia who have Ancestry DNA profiles.

So I thought the match might be through my husbands family who also lived in Wokingham, but there is no match with LM or BT. Nor with any of the many Langley family DNA samples on Ancestry.

But if my Dad has no common DNA with MR, then how did F and B get it from William Chaplin and Mary Trumplett?

Have I misunderstood how DNA works? You can only get DNA from your ancestors through your two parents and four grandparents. You can't randomly get 8cM outside of what your parents (or grandparents) have.

I have to say that the connection is not made in MR's tree, but by those connections that Ancestry makes through several other trees. The connection does seem feasible, but the DNA results don't gell.

I guess I am off to research through the records and chase down the connection.
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Old 26-09-19, 04:46
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At that size it sounds like a false positive. If your daughters match then either you or your husband has to also match.

With GEDmatch you can look at the segments can't you? Is it the same segment for both daughters?

If you and MR both have solid paper trails to William and Mary then I would say one of you has a NPE.
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Old 26-09-19, 09:29
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Presumably he isn't a match to you?
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Old 27-09-19, 08:52
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marquette marquette is offline
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I dont know if MR matches me, I have not found him on GEDMatch. I think I need to get myself on Ancestry.

I have checked out the paper trail, and it is correct, he is a relative through the 5ggps.
Then again, he could also be related to the Langleys, and I need to do more on that side. He might match with my husband, but not his sisters.

I think may it just one of those small matches "common to a locality" sort of thing, or a false positive.

BTW, I was quite surprised by the large variation in DNA matches between my two daughters. Maybe I should do a post about the differences I found, I could also do my sisters-in-law and husband as well. It might help everyone understand the range of cM matches you can have in a family.

Anyway, I am quite pleased to locate another descendant of this couple.

Last edited by marquette; 27-09-19 at 08:56.
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Old 12-10-19, 10:55
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So, I got fed up with trying to figure out DNA matches with no family trees and decided to play around with the groupings on Ancestry to see what else I could find out.

Firstly, I consolidated my Dad's DNA "common ancestor" or known matches into his four grandparent groups, with a couple of distinct subgroups. Then I looked at the shared matches of those matches.

Next I made colour groups for "Matches with F", "Matches with B", "Matches with R" and "Matches with P".

There are some quite surprising results.

Dad and F share 58 matches, while Dad and B, her sister share 66 matches; that's not too much difference, but their cousin shares 93 matches, one-third more. Dad and his nephew share 72. This surprised me because Dad and F share 2031 cMs and, with B its only 1745 and R 1623. (Nephew P shares 1980cMs)

The shared matches with R include a large group that only the 2 of them match with, a group largely in the USA, making me wonder if there might be a connection on her other (paternal) side.

Dad has 76 matches with known members of his Paternal family - 5 in the second cousin range who match with all 5 of our samples, 18 in 3rd cousin range who match with between 2 and 5 of ours. Many of the further-out cousins match randomly with P, F, B and R, some match only with Dad. Some of this depends on the generation - but who matches who seems totally random.

I can see a lot more comparing of matches in my future. I am hoping this might reveal where some of the distant matches fit in.
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