parents as "cousins" on #dna

Alexander Press

Hello all. Has anyone else had the experience of finding their parents identified as "cousins" on Mine are on the threshold between 4th-6th and 5th-8th at 20 cm shared over 5 segments. The shared matches cover multiple branches of their families. Perhaps if you take any two people of Eastern European Jewish ancestry there is a non-trivial likelihood that they will show up as "cousins." On the other hand, I have found that in every case of a documentable third cousin or third cousin once removed, Ancestry correctly identifies the relationship if it does not understate it.

Mark Strauss

Ancestry predicts that my wife and I are 6th to 8th cousins with 10 cM shared. I have slightly more with her maternal uncle. We have two very healthy and successful adult children. We also discovered that both of our maternal great-grandmothers came from Vilkaviskis, but have not found the paper trail linking our two families. Known surnames from Vilkaviskis in my family were Rousuk and Ephraimson. In her family, the family name was Ringel.

I also found a distant link on another branch of my mother’s family going back about 12 generations, where we have found a common ancestor with my wife’s paternal family:  Moses Auerbach, A family of scholars, the progenitor of which was Moses Auerbach, court Jew to the bishop of Regensburg, about 1497. He is my wife’s 13x Great-Grandfather and my 15x Greatfather.  Moses' daughter Gittel Isserles is my 14x great-grandmother and his son, Simon Wolf Auebach is my wife’s 12x great-grandfather.  

Alyssa Freeman

I've found that my parents are cousins by marriage before they got married to each other. I'm not clear on the whole 1st/2nd/3rd cousins once/twice removed, etc, but I'm guessing it's probably 7th or 8th cousins by marriage.
Alyssa Freeman
Henrico, VA


I recall reading that all Ashkenazim are, on average, 5th cousins of one another. Sorry, unknown source.
-Jim Gelbort

Jill Whitehead

Jim is quite right, it may even be closer than 5th cousin. Every person of Jewish origin supposedly shares at least one chromosome segment in common, however small. That is why I never look for cousins above 3rd to 4th cousin level on DNA sites. It is also usually impossible to match with the many 3rd cousins the sites will give you - I have thousands of 3rd cousins on FTDNA, 23andme, Ancestry and My Heritage, most not in common with each other. The sites are quite often optimistic in their assessments, and because our acestors lived in isolated communities and often married their cousins in the past, these relations can often appear closer on DNA sites. 

In recent family history terms, my great grandparents Benjamin (1855-1945)  and Janet (1859-1937) Brown (Brin from Vishtinetz, now Vistytis) from Edinburgh, Scotland were first cousins. There were many first cousin marriages in this family, who were of rabbinical heritage.  Benjamin's youngest son married Janet's nephew (her brother's son), making them double first cousins.

Also, Benjamin's son Morris (1881-1946) (my grandfather) married Leah Guttenberg (1887-1942) whose mother was Basha Plotnvosky. Basha's sister Rebecca married Solomon Berkowtiz (Karobelnik), whose daughter Annie Leah married David Lazarus Brown, first cousin of Morris Brown, son of Benjamin. This makes their descendants my double second cousins on both the Brown and Plotnovsky side.

This has some interesting DNA results, as the same generation descendants of Benjamin and Janet (first cousins) share a lot more DNA with me, than the descendants of  Benjamin's sister Janet Michaelson nee Brown, who was not a cousin of her husband.

Jill Whitehead, Surrey, UK

Shelley Mitchell

I’m fairly sure that most of the marriages within a family are arranged. My mother was supposed to have an arranged marriage with a first cousin. Unfortunately he was unable to leave Europe before the Holocaust.
Shelley Mitchell, NYC    shemit@...
Searching for TERNER, GOLDSCHEIN, KONIGSBERG, SCHONFELD, in Kolomyya; PLATZ, in Delaytn; and TOPF, in Radautz and Kolomea.


I was always told that my maternal grandparents were cousins, but I don't know to what degree.  I was told that my grandfather lived with my grandmother's family when he first emigrated to America at about age 13 as his parents did not emigrate.  I have no idea if I will ever be able to verify any of this.  I assume city directories and/or census might help, but so far no luck with census and no access to NYC city directories in the appropriate years.
Barbara Sloan
Conway, SC


"Endogomy" (Wikipedia):  Endogamy is the practice of marrying within a specific social group, caste, or ethnic group, rejecting those from others as unsuitable for marriage or other close personal relationships. Endogamy is common in many cultures and ethnic groups.

This makes the DNA match calculations very complicated.  

The well known author Maurice Lamm has an interesting article on Prohibited [Jewish] Marriages at the site that I found very informative:

-Jeffrey Lane, NY

Sally Bruckheimer

"Jim is quite right, it may even be closer than 5th cousin.". I once found who I thought was a 20th cousin, an Osorio in London. We exchanged gedcoms, and I was disappointed to find he was a 5th cousin in another line.

I also have a 3rd cousin, who is also his own 2nd cousin, and my 5th cousin, because his parents were 2nd cousins.  And I have a double 3rd cousin, because my grandfather and his brother married sisters, the boys aunt had married the girls uncle, so they had met before, at least one of the girls knew them. The sister came to the US and went to Missouri where the boys and her sister were, and quickly married the brother.

I also have an 8th ggrandfather who is my 8th ggrandfather 6 times, and a 9th ggrandfather, because his grandchildren and ggreat grandchildren all married each other. And I could go on.

Sally Bruckheimer
Princeton, NJ

Crivorot, Sergio

​My grandfather married his niece, that is, my grandmother was the daughter of his sister. 
This makes a very curious tree design. On the other hand, it saves time when doing genealogical work as I have less distinct family branches than most people.
Sergio Crivorot
Bessarabia - Krivorot, Lipovetsky
Poland (Opatow, Opole, Ostrowiec) - Wroclavski, Wajc, Zylberstajn, Wajnbaum, Laufer
Sent with BlackBerry Work (

Lee Hover

I have a first cousin, Arlene,  who married our mutual first cousin. Her parents, Bernard and Esther, were also first cousins. Bernard's parents were also first cousins. And I suspect that one of his parents was also the result of a cousin marriage.  This makes for a very tangled tree, and I often say that the old song "I'm My own Grandpa" was written about my family. Try explaining that your Uncle was also your cousin and so on.  In the case of Arlene, her aunt was also her mother-in-law.   And, no, the family was not orthodox.

Sally Bruckheimer

"I have a first cousin, Arlene,  who married our mutual first cousin. Her parents, Bernard and Esther, were also first cousins. Bernard's parents were also first cousins. And I suspect that one of his parents was also the result of a cousin marriage."

Arlene is the explanation of endogamy, for anybody who needs one.

Sally Bruckheimer
Princeton, NJ

Alexander Press

Just a quick follow-up regarding Going over my niece's list of shared matches, I was able to check several documentable fourth and fifth cousins, all correctly identified as such on Ancestry. From this I gather that a "4th-6th cousin" or a "5th-8th cousin" may be just that and not some phantasmic relationship. On the other hand, I have found 23 and Me virtually useless for establishing relationships. Whereas Ancestry sometimes understates them (e.g., a third cousin identified as "4th-6th"), 23 and Me clearly overstates them. Thus I would avoid lumping the two services together. Ancestry is actually so good that I wish it could be a bit better, but my hunch is that it provides enough information to allow a skilled codebreaker to cluster the matches along discernible branches even with the interference created by endogamy. One complaint I have is that there's a mysterious canyon between 90 cm and 60 cm, which customer service has been unable to explain.


I think we have to be careful comparing results of testing companies. Unless you test most of your cousins with all the companies, there's no way of knowing which is better. You certainly can not just go by which turns up more documentable cousins. There are all sorts of reasons why someone might turn up as a cousin without you really having a clue as to how they relate. Endogamy is one, but just the fact that surnames churn over frequently, especially with women upon marriage makes it hard to even identify someone with a branch you already know of. Also, adoptions, informal and formal. I'm also discovering that a significant number of men on my tree (several percent)  especially those who were about 30 in the 1950's or early 1960's, had children out of marriage. Also, at least in one case, relatives back in Poland converted to Catholicism in the 1900's (making them unrecognizable as relatives just by given names and surnames...except that their names now were very Polish looking, so that clued me in....). 

Just as anecdote, I did discover that a 4th cousin of my father was a known client of his! They had a laugh over that. But that's the only case in my tree. Though I do see some endogamy among relatives, I haven't see any with my direct ancestors.  And though one test long ago before some chip changes and algorithm changes, my parents showed as cousins, I don't think they do any longer. Considering my genealogical details, it seems very unlikely that they are closer than 6th cousins, but I'd guess 7-10 is more likely to be correct for them and most Ashkenazim. For the few with documentable distant rabbinic lines, I can see that a few 15th cousins married, but they may very well have cousinhoods that are closer than the ones I can document. 

Steve Bloom
Central Virginia

Nicole Heymans

There are two issues in this thread: a) endogamy and b) DNA bias.
a) Endogamy is not peculiar to Ashkenazi Jews. In the past, most folks married within their own village, and marrying a cousin was not uncommon. In my mother's (Jewish) ancestry, one of her maternal aunts married a first cousin; and her father CL had a "double second cousin" CDL: their fathers were first cousins and their mothers also. And CDL had two daughters who married two brothers. One way of marrying "in the family" while avoiding inbreeding.
On my father's side (not Jewish) I also find a brother and a sister of Granny W marrying two McI siblings.
And I remember a friend who was working on a thesis about intermarriages in "local isolates" - I envisioned distant places far from civilisation, but he was working on communes of Brussels which were villages 5, 10, 15 km distant in the 19th century.
b) Bias. In the past there was an interesting helpfile on FTDNA explaining some essentials of statistics: what a cm means, how the amount of shared DNA decreases, the spread of this amount increases with distance to shared ancestor; and there was a table of likelihood of detection according to distance of relationship. From memory, 50 % for 4th cousins. Some will be detected as "5th-distant", some not at all, others as closer than reality. As the true relationship becomes more distant, likelihood of detection decreases, and only the leading end remains. A tiny percentage of an enormous pool, a vast majority of our matches.
If it's any consolation to patrons of this discussion group, the situation is no better on my non-Jewish side.

Nicole Heymans, near Brussels, Belgium

I agree with Nicole Haymans and want to add my own experience.  My paternal grandfather married his half-niece, my paternal grandmother, in 1919 in Providence, Rhode Island.  My paternal grandfather's half-sister was my paternal grandmother's mother.  They married in Rhode Island because their marriage was legal there since it was allowed under Jewish law, but illegal in New York City where they resided.  Peculiarly, under Jewish law a man is allowed to marry his niece but is not allowed to marry his aunt.


My father’s parents were first cousins, and one of his sisters married a first cousin. They all lived in the same shtetl, Lyachavichi, near Baronovichi, in what is now Belarus. I have been able to trace their names back to the 1700’s and have found tax records from the 1850’s.

Jules Levin

On 7/9/2020 12:21 PM, karen.silver@... wrote:
IThey married in Rhode Island because their marriage was legal there
since it was allowed under Jewish law, but illegal in New York City
where they resided.  Peculiarly, under Jewish law a man is allowed to
marry his niece but is not allowed to marry his aunt.
Even more peculiar is that Moses was the product of an aunt-nephew
marriage.  The rabbinical explanation is that it happened before the law
was issued at Sinai.  Still, the pre-Sinai observance of laws by
Abraham, Isaac, and Jacob are favorably noted.

Jules Levin

Todd Leavitt

My wife and I share 85 cMs of DNA. The likely  MRCA would be someone from Bialystok, where both of our maternal lines resided. I concur with the challenges created by  Ashkenazi endogamy. One of my FTDNA kit reflects more than 30000 "cousin" matches! Unless the match exceeds 175 cMs (and at least a 20 cM longest block] I have never succeeded in connecting the dots to the individual.
Note that GEDMatch has a utility that will "predict" if your parents are "related" .

Lee Hover

Re my entry above:  Arlene's parents, who were first cousins, lived in New York City.  They also had to go out of state to marry.