Speculation invited.

[Galium]

I hope this isn't too complicated, but here's a thing.

OH's GGgrandfather married twice. 1st wife was Mary Ann; 2nd wife was Emma. OH is a descendent from the second marriage.

 Mary Ann and Emma  were not related to one another.  As far as I know Mary Ann's family lived in Gloucestershire for several generations; Emma's father came from an unspecified place in Germany, and her mother's family seem to be long time Londoners.

OH has two DNA matches (18cM and 6cM) descended from Emma's brother John, and one - DM - descended from Emma's sister Caroline (26cM). John's descendents don't show up as shared matches with DM.

Ancestry has no matches with anybody also descended from Emma.

OH also has two matches (45cM and 11cM) who are both descendents of a granddaughter of GGgrandfather and Mary Ann.  These show up as shared matches with others from GGgrandfather's family -  but also with DM.

Am I missing something, or is the simplest explanation for this the one that I think it is?

[Eric Hatfield]

Hi, I'm not sure what you think is the simplest explanation, but I think it all fits together.

If I have drawn up the family tree correctly, and assuming all the matches are to people in the same generation, then OH is 3rd cousins with the matches from Emma's siblings and half 2nd cousins with the matches from Mary Ann.

Using the figures in the Shared cM project (2017) by Blaine Bettinger, the expected range of matches for these relationships is:

• 3rd cousins: 0-217 cM (average 74)
• Half 2nd cousins: 9-397 cM (average 117)

The matches you report are within those ranges, though generally at the lower end of them. I suppose this is a little surprising, but that's sometimes how things work out. (If some matches are different generations, then these figures would be different.)

You don't give the cM values for the other matches. Are they similarly low?

I'm thinking the thing to do would be to put all the matches in a chromosome browser if you can and see if they triangulate (if some or all are with Ancestry, export them all to Gedmatch). If they do, then it is clear that the relationships are as you have described them. If not, the answer isn't so clear.

I'm no expert, so others may have a better understanding.

[IJDisney]

If I understand right, you are asking why DM seems to link with descendants from your grandfather through both wives (Emma and Mary Ann), but does not match with other members of Emma's family?

The chance inheritance of DNA can explain the latter point. 2nd or 3rd cousins do not have to have DNA matches with each other since in theory they only inherit about 6-12% of their DNA from their common ancestor. You have inherited 'different bits' of DNA that match two other sets of 'different bits'.  of DNA, but those two other sets of 'different bits' don't match each other. That is not unusual. And if John, Caroline and Emma were not full siblings (i.e. one or both of their parents had them by different spouses), that would make the chances of common DNA even less.

Regarding the apparent connections of DM to your grandfather's two wives - have you considered that your grandfather was related to one of Emma's parents? Or maybe John's wife was related to your grandfather or to Mary Ann? Or that the grand daughter of Mary Ann was married to, or had a parent who was related to, someone from Emma's family, or even to John's wife's family? Or maybe one of DM's parents was related to your grandfather, or to Mary Ann.

There is no simple answer - only more research.

[Galium]

Hi Eric Hatfield and IJDisney. This is just to thank you both for your thoughtful replies, and  to let you know that I'm still thinking about it, so hope to be able to reply more fully later.

[Galium]

Hello again. Still puzzling over this one.

1. OH's two matches descended from GGgrandfather and Mary Ann who share DNA with DM are uncle and niece to each other. (Surprise in this is that the uncle, SH (half 3rd cousin to OH) is the match sharing 11cM; his niece DH (half 3rd cousin 1x removed to OH) is the match sharing 45cM).

2. The only other match  from GGgrandfather's 1st marriage is another half 3rd cousin (23cM), descended from a different child of GGgrandfather and Mary Ann. This person is not a shared match with DM.

3. All other matches from GGrandfather's family descend from his siblings, or from further back. Many of them match with the descendents of Mary Ann.  None of them match with DM, or with anyone else connected to Emma's family.

4. I am very doubtful that GGrandfather was at all related to Emma's family, both from the paper trail which goes back to the 17thC for him, and for geographical reasons - but of course it can't be ruled out entirely.

5. Mary Ann's daughter, from whom the two matches to DM are descended, married a Scotsman, from a Scottish family. Again, geography tends to rule out a connection between him and Emma's family.   Her daughter married a missionary from the West Country, and settled in the US, where the ancestor of SH and DH mentioned in paragraph 1 married someone from a German family.

5. It's possible that Emma's German father was related to this family (they don't share a surname).  I have never been able to discover where he came from, although looking at the trees of the closest matches that OH has who have German ancestry tends to indicate that he came from somewhere in or near the Alsace region. 

6. However, as far as I can see, the ancestors of SH and DH came from a place east of Berlin, near the Polish border, and hundreds of miles from Alsace. Of course there is nothing definite about the Alsace origin idea, so I can't rule out a connection in Germany, but neither is there any obvious link.

7. Emma's brother John was a full sibling, but a lot older. Two  matches descended from him are a 4th cousin (6cM) and 4th cousin 1x removed (18cM).  So as IJDisney says, perhaps it isn't significant that they aren't shared matches with DM, or with SH and DH. On the other hand if they were shared with SH and DH, it would point more strongly to a common ancestor from Germany.

8. Ultimately, on the face of it DM, as a descendent of Emma's sister Caroline should not have common ancestry with descendents of GGgrandfather's first wife.  The simple explanation that came to mind was that GGgrandfather was the father of Caroline's eldest son (at the time he was born she had been married for about two and a half  years).

Use of a chromosome browser would help, but currently not feasible.

And comparing photos of GGgrandfather and his wife's nephew doesn't quite rule it out.

https://i.postimg.cc/Jz80psm4/CG.jpg
https://i.postimg.cc/J09mD27z/LM.jpg

[Liz_in_Sussex]

Hi,

I have read this - and reread it several times - and then drew up a little pedigrees with all the bits of DNA to see where I got to.

Firstly, I would absolutely agree about the small / seemingly inconsistent amounts not to be too much of a concern as at this level it's entirely possible not to share any.

I cannot come to any conclusion though, other than the one you yourself have - that Caroline's child was fathered by the same man as Mary Ann's - were they living nearby - presumably this was all happening at the time of the censuses - so is it POSSIBLE as far as location that he is the father?

I don't know if any of the tools on DNApainter would help - I've not used it much - but a lot of people swear by it for solving mysteries.

Liz

[Eric Hatfield]

Hello again. It certainly is intriguing, and I'm not expert enough to say much. But a few thoughts (you invited speculation!):

You have four groups of matches (using initials and/or cM to identify) - hope I've got this right:

1. A descendant of Caroline (DM-26)
2. Two descendants of John (6 & 12) - don't match with DM.
3. Three descendants of Mary Ann (DH-45, SH-11) - two match DM, one doesn't.
4 . A bunch of descendants from GGF's siblings or parents - generally match with #3 but not DM.

It seems to me that your conclusion (GGF may have fathered a child with Caroline) is supported by facts #1-3. But does #4 fit? GGF would share significant DNA with his siblings, parents and grandparents, so on your hypothesis, you'd expect #4 to match with DM. But they don't. Now of course, we are talking about 4-6 generations back to a common ancestor, so the DNA may have been diminished too far to show up. But would that occur in all of the people in #4?

This would lead me to at least wonder if there was some other connection, between one of GGF's relatives and C's relatives.

I agree with Liz that DNA Painter could help, but it requires segment info, same as a chromosome browser. So I still think getting all the DNA you can into Gedmatch and using its browser is going to be necessary. Then you could see who triangulates and who doesn't, and you could use DNA Painter to assist in this.

If you don't have control of all the samples, as I presume, then this would require asking others to do the transfer, or you offering to do it on their behalf. I have found even distant relatives that I didn't previously know willing for me to do that, but of course every circumstance is different.

But like I said, I am just an amateur, and maybe I've got the wrong end of the stick in some of this. But maybe that speculation will help in some way.

[IJDisney]

What relationship is DM  to OH?

Do you know what the cM matches are between DM and DH/SH?

[Galium]

Hello, Eric Hatfield, IJDisney and Liz. 
Thank you all very much for giving this your attention, and for your replies.  I am sorry for not having responded sooner, and I apologise sincerely for that. I know how disheartening it is when somebody doesn't reply.

It turns out that the answer was something that I hadn't really considered, and wouldn't have until Thrulines adjusted - and showed me that DM is descended from Emma via a different child than OH's ancestor, as well as from Caroline.  That is, a Ggrandchild of Emma and GGgrandfather married a Ggrandchild of Caroline, and DM is a descendent of that marriage.

So, the mystery is solved and OH's GGgrandfather is exonerated (and also owed an apology).