Cousins in Common

The prior article concerned DNA cousins in common.  Finding DNA cousins who match you and some of your other DNA cousins is not uncommon.  You must be careful in drawing inferences in these situations.

Finding cousins in common is a tool at FamilyTreeDNA and GedMatch.  You can manually compare cousins at 23andMe to ascertain if someone matches your cousin- as long as everyone is sharing genomes.  The glitch arises when two of your cousins match each other, but not on the same segments of DNA where you match each of them.

The query:  If three people share different segments of DNA with one another, are they related through a common ancestral line?

Answer:  Maybe, maybe not.

Unless the match is very close, I don't pursue cousins in common.  Early on in my genetic genealogy pursuits, I was overwhelmed with my mother's DNA matches.  They matched her and her other DNA cousins, though not on the same segments.  To this day, I have no direction in this undocumented branch of her family tree.  These cousins either live in or have recently immigrated from Eastern Europe.

Two years ago, my maternal third cousin appeared among the matches at 23andMe.  We share a pair of great great grandparents, John Preston (1857-1928) and Bridget Sheehey (1857-1916).  John was born in Dutchess County, New York to Irish parents.  Bridget was born in Ireland.  (I have no idea where in Ireland they lived.)

Here is the graph of his shared DNA with my mother- three segments:

With this new close cousin's DNA, I compared him to my mother's distant DNA cousins to round up some people that we could place in the Preston/Sheehey branch.


Comparison of my mother's distant DNA cousins from Eastern Europe revealed that this Irish Preston/Sheehey cousin matched a lot of them on multiple segments.  Lots of cousins in common, but from different branches of their respective trees.  To date, no DNA cousin from Eastern Europe matches my mother and this Irish Preston/Sheehey cousin on the same segments.

The point is to be cautious when looking at cousins in common who do not share the same DNA segments.

Cousins of Cousins

A DNA cousin at 23andMe shares identical DNA with my father and three of his close cousins- each from a different branch of the tree.  This is why you need to see the segment(s) shared between DNA cousins and you need to test your own close cousins to narrow down which branch of your tree may hold the common ancestor.

The match to my father will be in his Duryea and Cummings branch because the segment of DNA is shared with the cousin from descended from Abraham Brewer Duryea (1878-1944) and Nellie Cummings (1879-1965).

The segment shared between the DNA cousin and the cousin from the Uhl and Patschke branch could match anywhere in the cousin's entire family tree.

Same for my cousin from the Cook and Neal branch- the common ancestors could be anywhere in his tree (but not too far- they may be about fourth cousins).  Matching my father does not narrow down the possibilities because my father's shared segment with this DNA cousin can be attributed to another branch.

I cringe when people write to me about DNA cousins in common when they don't match on the same segment.

Family Tree Repair

John R Winterton was born around 1831 to Samuel Winterton and Sally Ann Johnson in New York City and died February 18, 1890 in Keyport, Monmouth County, New Jersey.

Here are the possible matches at Ancestry through Family Tree Maker:

Entries with a green arrow are dates of death consistent with the death certificate.

These are all derivative sources.

With the prior date of death from Find A Grave, 13 February 1896, I searched for a death certificate at the New Jersey State Archives and found none.

The memorial page for John R Winterton shows a side view of a stone that is not easy to read.  This is why you should transcribe a stone while physically accessible, and not later by looking at a picture of the stone.  The font shapes all of the numbers the same and differentiates them with a small piece missing.  It is very easy to mistake one number for another.

I visited Green Grove Cemetery in Keyport and took frontal pictures of the stone.  The date of death is etched as Feb. 18, 1890.  The lettering is not easy to read in the best of the pictures.

This date led me to a death certificate an an obituary in the Red Bank Register.

The death certificate is not easy to read.  The "body was found" on February 18, 1890.  This must have been an unwitnessed death, likely a heart attack.  He was 58 years old.  It may be possible that John died the previous day, did not come home, so a search party was sent out at daybreak on February 18th.  None of this is stated on the death certificate or newspaper obituary, so we'll go with a date of death on February 18th- when the body was found.

John R Winterton, a farmer living near Matawan, was found dead beside the railroad track near that place on Tuesday of last week.  He had fallen dead from heart disease.

I contacted the person managing John R Winterton's memorial page at Find A Grave.  The date of death was corrected.  I contacted the owners of the family trees who used the erroneous date.  So far, only one changed the date.  The other two continue to use the incorrect date of death.

The collection at Family Search -  New Jersey, Deaths and Burials Index, 1798-1971 - has the correct month and day, but the year is off by one.  This is an ongoing issue with this particular index and serves as a reminder that indexes are not primary sources.

An index for deaths is being created at the Archives.  Their index has the correct date of John R Winterton's death.

You need to be very cautious when straying from primary sources.