BackgroundAll living persons and test subjects have been anonymized for privacy reasons.
In this particular study, AncestryDNA performed all DNA tests.
Abstract
A client took an AncestryDNA test to investigate the pedigree of their Great-Grandmother. The outcome was not as anticipated!
Introduction
Our client's Great-grandfather, Samuel Albert Thompson ostensibly had eight children by two wives: five children by his first wife and three by the second.
Our client (MS) reported that little was known about wife #1, from whom the client was descended: no photographs, few primary sources, and no death record. The client reported that their grandfather said that little was spoken about his mother, Jennie Telfer, and no one living appeared to have any idea as to the circumstances of her death or what precisely happened in this regard. Discovering New Ancestors was engaged to investigate as best we could, using traditional research methods and the results of the client's AncestryDNA test.
The client's DNA matches suggested that four direct descendants of Samuel Albert Thompson had already tested: two Grandchildren of Samuel Thompson (AT and DT) and two Great-grandchildren (RB and MS):
As subject RB is descended from Samuel's second wife, he would appear to be a half-relation to the DNA test-takers descended from Samuel Thompson and his first wife. This would suggest that one strategy would be to use our CMA process to curate a set of In Common With DNA matches shared by AT, MS, and DT and then to exclude from this collection matches shared with RB, presumably leaving a collection of siginificant DNA matches connected to our client through the ancestors of Samuel Thompson's first wife.
Preliminary Analysis of Shared Linkage
We began our analysis with RB and MS — the two Great-grandchildren of Samuel Thompson by different wives — whom we would expect to be half-2nd cousins. However, (per the Shared cM Project) the 371cM of DNA shared by RB and MS significantly exceeds the amount of DNA half-2nd cousins would be expected to have in common, suggesting that RB and MS are actually full-2nd cousins, sharing 2 Great-grandparents. Since RB's grandmother was born 7 years after the last of Samuel Thompson's children by his first wife, it's reasonable to conjecture that MS's grandfather was also born of Samuel Thompson's 2nd wife, the fact that his middle initial (T) stood for Telfer, the family name of Samuel's first wife.
If RB and MS are full-2nd cousins, — presumably ahring Samuel Thompson and his 2nd wife as common Great-grandparents — then we would expect that DT would no longer be MS' first-cousin once removed, but would rather be a half-1C1R. However, the 514cM of DNA shared by MS and DT are well beyond the reported limits of the half-1C1R relationship.
Finally, we turn to DT and AT, the two tested grandchildren of Samuel Thompson and his first wife. We've already established that DT, MS, and RB are all full-relations, sharing both Samuel Thompson and (presumably) his 2nd wife. If DT and AT are full-first cousins, then all of our tested subjects are descended from Samuel Thompson and the same wife; otherwise, a half-cousin relationship between DT and AT would indicate that AT is indeed descended from Samuel Thompson and wife #1, while our other subjects are descended frm Samuel Thompson and wife #2.
Analysis of the 914cM of DNA shared by DT and AT, suggests that, in all liklihood, DT, AT, and the other Thompson cousins tested thus far are all descended form Samuel Thompson and the same woman.
Although the 914cM shared by DT and AT allows for a slim possibility that half-first cousins, the Shared cM Project indicates that the same linkage provides for a much greater liklihood that DT and AT are full-first cousins.
Further Analysis
The DNA tests of our four individuals ostensibly descended from Samuel Thompson's two wives strongly suggests that Samuel's two wives were either closely related or in fact the same individual.
If Samuel's two wives were sisters, then their offspring would be three quarters-siblings, which might account for the above-expected linkage shared among their descendants, although we would expect the amount of this surplus linkage to be reduced over the intervening generations. However, Blanche Jane Tiffault's immediate family doesn't provide us with a likely candidate to have assumed the alias of Jennie Telfer — other than Blanche herself.
Since three of Jennie Telfer's five biological children appear to be descended from Samuel's 2nd wife (Blanche Tiffault), it would appear that, at minimum. all of Samuel Thompson's offspring born after 1912 were born of Blanche Tiffault. It would be useful to have the descendants of Samuel's two eldest children (Viola and Allen Thompson) test their DNA so as to determine their connection to the Tiffault family, or lack thereof.
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