First Close Relative for Haas and Zolder lines

A close match appeared at Family Tree DNA among my maternal uncle's matches.  This is the first close match from his father's side of the family.  The common ancestors are Samuel Haas (1867-1945) and Mary Zolder (1870-1948).

Use of a full name is encouraged at Family Tree DNA.
Unlike 23andMe, FamilyTreeDNA testers do not have to "consent to share genomes" to view the matching DNA segments,
while AncestryDNA does not show shared segments.

The only information about this match is his name, email address, and the amount and location of identical DNA.  This was enough to figure out how he is related to my uncle:  they are first cousins, once removed.  This cousin is the generation after my uncle, though my uncle is younger than this cousin.

Family Finder Chromosome Browser

Here is a graph that Family Tree DNA can create for a physical representation of the identical segments shared by relatives, called a Chromosome Browser.  (23andMe also creates such graphs.  AncestryDNA does not.)

The orange lines are the segments shared by my uncle and his first cousin on his mother's side of the family- ODonnell and Preston.  The blue lines are the segments my uncle shares with the first cousin, once removed, from his father's side- Haas and Zolder.

Note that in some areas, such as chromosome 11, that both cousins appear in the same areas.  This is because every person has two pairs of chromosomes numbers 1 through 22.  One came from the mother; the other from the father.  Current DNA analysis does distinguish which side the segment is on.

For distant DNA cousins, usually only one or two segments are shared.  Other people will often share the same spot on a chromosome.  If they do not match each other, this means that one is from the mother's side and the other from the father's side.  (Unless the segments are too small to report, or there is an error in reading the DNA in that spot.)

Samuel Haas and Zolder were from what is now Slovakia.  They spoke German.  There do not seem to be many of their relations in the DNA matches of my uncle.  Family Tree DNA provides and "in common with" tool.  Out of the 400+ matches to my uncle, only three also match his new close paternal cousin.  In comparison, seventy matches are shared by my uncle and his maternal first cousin on their common Irish lines.  Certain populations are more numerous than others in the DNA databases.

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.