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Unknown Great-great-grandfather found? Do the cM fit?

borum1
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Hello,
I recently saw that I have numerous matches with one family line coming from the same village as my out of wedlock born great-grandfather. I investigated where the ancestors came from and they were practically neighbours, with the father of the individual being in all trees being in the right age for having some kind of relatinship with my great-great-grandmother.
But in theory it could be one of the uncles, not the father too. However, the matches point to minimum a 3rd half cousin. The highest matches are:

1st match: 148 cM in 8 Segmenten (grandsons child)
grandson of 1st match = 16 cM in 2 Segmenten

2nd match: 125 cM in 8 Segmenten (granddaughters child)
kid 1 of 2nd match = 65 cM in 4 Segmenten
son of 2nd match = 55 cM in 5 Segmenten
grandchild of 2nd match = 60 cM in 3 Segmenten

There are additional high matches in the same range, like 60 cM in 3 Segmenten.

How are the chance with so many close matches that the person was not my great-great-grandfather, but instead one of his brothers or brothers in law was the father? This would reduce the genetic relationship on averag about 50 percent, but the relationship is already high for a half 3rd cousin, isn't it?

Any help and opinion would be most welcomed.

ericdubois
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I admit I don't really understand the way you present the matches. I suggest you try your theories on the "What are the odds" tool on DNA Painter.
https://dnapainter.com/tools

borum1
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ericdubois ha scritto:
23 ottobre 2020, 21:15
I admit I don't really understand the way you present the matches. I suggest you try your theories on the "What are the odds" tool on DNA Painter.
https://dnapainter.com/tools
I did use those, but thank you very much for the link. My real question is, whether the main matches could be anything less than half 3rd cousins? What are the odds for two such high matches?

Using the tool for the lower main match:
48% Half 2C 2C1R Half 1C2R 1C3R
25% Half 1C3R † 3C Half 2C1R 2C2R
14% Half GG-Aunt / Uncle 2C Half 1C1R 1C2R Half GG-Niece / Nephew
10% Half 3C 3C1R Half 2C2R 2C3R
3% 4C Half 3C1R 3C2R
~ 0% ** 1C1R
I have two matches and the relatedness decreases proportionally. I really ask this because I want to be fairly sure if adding that person to my family tree. Going by my investigation, they were practically neighbours and in the right age, and its either this person, or his brothers or brothers in law, yet a brother or brother in law would result in a lower match than half 3rd cousin. This is why I want to get a confirmation by experienced members that a relationship lower than half 3rd cousin is nearly impossible with these matches.

ericdubois
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borum1 ha scritto:
23 ottobre 2020, 21:58
I did use those, but thank you very much for the link. My real question is, whether the main matches could be anything less than half 3rd cousins? What are the odds for two such high matches?
The numbers in the charts are averages and normal ranges, but it's not unusual to have a match that falls outside of those ranges (either higher or lower) just because of the random way DNA passes down through generations.

For example, my wife matches 3 siblings. She shares 75cM with two of them and 144cM with the third.

borum1
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ericdubois ha scritto:
25 ottobre 2020, 01:06
borum1 ha scritto:
23 ottobre 2020, 21:58
I did use those, but thank you very much for the link. My real question is, whether the main matches could be anything less than half 3rd cousins? What are the odds for two such high matches?
The numbers in the charts are averages and normal ranges, but it's not unusual to have a match that falls outside of those ranges (either higher or lower) just because of the random way DNA passes down through generations.

For example, my wife matches 3 siblings. She shares 75cM with two of them and 144cM with the third.
What's her relationship with these matches?

ericdubois
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3rd cousin once removed. That relationship an average shared DNA of 48cM and a range of 0 to 192cM. So in this case the match is a little above average for two siblings and near the top of the range for the third sibling.

ericdubois
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I'm re-reading your first post. If I understand, your theory is that the common ancestor is your great-great-grandfather and the great-grandfather of match 1 and 2. That would make them your second cousins once removed, their children third cousins and their grandchildren third cousins once removed.

If we look per generation, that gives
relationship | avg | range | matches
Half 2C1R | 66 | 0-190 | match 1: 148, match 2: 125
Half 3C | 48 | 0-168 | match 2a: 65, match 2b: 55
Half 3C1R | 37 | 0-39 | match 1aa: 16, match 2aa: 60

All of the numbers are above average for that relationship but all but one fall within the range. It's possible that a little extra DNA comes from another common ancestor further back, or possibly an IBP segment.

To answer your question, your theory is definitely plausible based on the shared cM numbers.
Screen Shot 2020-10-24 at 9.10.14 PM.png

borum1
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Thank you, that helps. I have so far 8 matches from this person, of which 6 are in the highest percents for the relationship. Even if more distant matches contributed as well, there seems to be no other explanation but him being my great-great-grandfather.
His son moved to the USA and I can exclude any other relationship which could be close enough.

ericdubois
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If you go strictly by the odds, it would suggest that those matches are closer to you by 1 or 2 degrees of separation. But that seems to be often the case.

Out of curiosity, where did those ancestors live?

borum1
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ericdubois ha scritto:
25 ottobre 2020, 14:40
If you go strictly by the odds, it would suggest that those matches are closer to you by 1 or 2 degrees of separation. But that seems to be often the case.

Out of curiosity, where did those ancestors live?
In Southern Bohemia, region of Budweis and Krumau. The village is Rimove (Rimau) and the local population was Czech, with some of the neighbouring villages having been German and there was some intermarriage. I checked the records for the great-great-grandfather and his wife, as well as for the wife of his son for 2-4 generations backwards and there is no other hit. But looking at the records, its very likely that there are many distant shared ancestors, because the names and house numbers being repeated in the church book again and again, with the vast majority of marriages happening within the same village and 1-3 neighbouring ones.

ericdubois
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It's not unusual for people to immigrate to the same place where other neighbors or family members have migrated before them, essentially re-creating their neighborhood in another country. So it's very possible that your matches' father or grandfather married someone in the US with ancestors in the same region of Germany, which could add a little more shared DNA.

borum1
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That's true, they even have a Czech gravestone in the USA. His son married a woman from the region, but I have no known ancestors from that village or those of her ancestors for 2 generations back.
Their daughter was the mother of one of my highest matches, but on his paternal side, there is no overlap either for three generations, then the record is incomplete, but chances remain low. Same for the kids of the first half 2nd cousin once removed with 128 cM, so everything should come from the village Rimau and his great-grandfather to the USA.

I also have the tree for the highest match at 148 cM in 8 segments and there is again no overlap in the last generations, but the maternal side is from Alsace and I have known ancestry from Lorraine and Saarland, highly likely also from Alsace and South Western Germany. So there could be a small contribution from distant common ancestors from this side too, as well as from the village people in Rimau. My great-great-grandfather would be her great-grandfather. So she would be a half 2nd cousin once removed with possible additional shared ancestry from both sides of the family.

borum1
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Update: I have now 16 significant matches from that ancestor, with an additional match at the 2nd cousin once removed level. She shares 174 cM at 7 segments.

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