When the Family Tree of a DNA Match and Shared DNA Matches Don't Add Up

 I have a 3rd cousin-ish DNA match (47 cM in 6 segments) with a person that I will call Jane for privacy reasons.  AncestryDNA thinks this is a 4th to 6th cousin, perhaps due to the number shared segments.  I also have a number of known 3rd and 4th cousin matches that also share DNA with Jane, and 11 of them are AncestryDNA ThruLines.  Jane also has a small tree (less than 12 persons), even back to great-grandparents on one branch.  

Several years ago, I dutifully input the people in her tree into my DNA Research (quick-and-dirty) tree on Ancestry and research it back 5 or 6 generations, and nothing popped up.  Hmm - I thought "well, there are six small segments, perhaps the common ancestors are further back in time."  And gave up on it for the time being.

And along comes the new AncestryDNA Enhanced Shared Matches (I call them Shared Matches of Shared Matches - SMOSM) tool to help me figure this out.  The SMOSM for Jane and me include:

• A 2nd cousin 1x removed to me with 54 cM, and 1300 cM to Jane, that is likely the Grandmother or Aunt of Jane.  That really helped me identify Jane's probably grandparents.
• A 3rd cousin 1x removed to me with 30 cM, with 469 cM to Jane, that is likely a first cousin 1x removed , and is the daughter of the person above, per SMOSM.
• A 3rd cousin to me with 77 cM, and 35 cM to Jane, that is likely a 3rd cousin 1x removed to Jane.
• A 3rd cousin to me with 42 cM, and 274 cM to Jane, who is likely a 2nd cousin to Jane.
• A 3rd cousin to me with 32 cM, with 801 cM to Jane, who is likely a first cousin to Jane.
• A 3rd cousin to me with 28 cM, and 692 cM to Jane, who is likely a first cousin to Jane.
• A 3rd cousin to me with 16 cM, and 948 cM to Jane, who is likely a first cousin to Jane.
• And there are several more relative close matches.

I have identified the common ancestors as one set of my 2nd great-grandparents, through my great-grandaunt who is the great-grandmother of Jane, and the grandmother/aunt of Jane who is my first cousin twice removed, and the grandmother/aunt's six children, one of whom is the first match on my list above (so she is an Aunt to Jane, and still alive), and some of their children too (many of whom are living).  Unfortunately, there is no SMOSM with Jane which indicates that they are a sibling or half-sibling to Jane, which would be definitive at least for one parent. 

Here is a family tree that shows a similar relationship:

I can't find any record, or an obituary of any of those family members, that names Jane.   

My conclusion is that Jane is my 3rd cousin and our common ancestors are my known second great-grandparents.  

I am left with the very real probability that Jane was adopted as an infant and, although all of these folks are related, she may not know how or why.  Life happens!  And we know that DNA doesn't lie!

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