What is the relationship between my parents?
By Norbert Weinberg
Many years back, I started investigating my family tree, as I
knew that both my parents were descended from major rabbinic families. That
ancestry included the family of Rabbi Yomtov Lippmann Heller and the family of
Rabbi Akiba Eiger. I also knew that my parents shared a common three and four
generations above. This is the family chart, adapted from Geni.com.
The top blue line traces the ancestry path from myself, Norbert
Weinberg, through my father, Willaim Weinberg, then his mother, Binah
Zarwanitzer, and finally, his grandfather, Moses Zarwanitzer. The bottom blue
line traces from myself, through my mother, Irene, nee Gottdenker, through her
father, Norbert (Nachman) Gottdenker, through his mother, Sossia Gottdenker,
the daughter of the aforementioned Moses Zarwanitzer. The red line indicates
where the same ancestor sits on the two lineages.
In short, my father’s grandfather is my mother’s
great-grandfather, albeit from different wives.
The black lines
indicate lineage from prominent Rabbinic families – Kahana (descendants of R.
Yom Tov Lippman Heller) and Eger ( Iger, Eiger, descendants of R. Akiba Eiger).
I posted my DNA kit to a program called gedmatch.com, which
has a variety of research tools not available on other genealogy websites. I asked
the program to run an “Are your parents related” test.
“What this tool does
Are Your Parents Related analyzing one DNA kit for long
homozygous regions, also called ROH. These are areas where both copies of a
person's DNA are unusually similar. When a person has large or repeated ROH
regions, it may suggest that their biological parents share a common ancestor.”
The results?
“This analysis suggests the person's parents are probably
related.
- Largest
reported segment: 26.7 cM
- Total
reported ROH > 7 cM: 91.1 cM
- Reported
regions: 6 “
Then it may this assessment:
“Based on 91.1 ROH shared cM. …
Relationship Type
and Estimated Probability
3C Group (Third cousins)
37.5% but also 2C2R (2nd cousin twice
removed) Half-2C1R (Half-2nd cousins once removed) and Half-1C3R (Half
1st cousins, thrice removed).
2C1R Group 29.2%, 3C1R Group 18.0%.
I queried Google AI
to explain these terms based on my chart and test results:
“I have noted those branches of your family tree. When
relatives share only one common ancestor (like a grandfather) instead of a
couple (both a grandfather and grandmother), the relationship is prefixed with half-Relationship
Name. Because your parents descend from different wives of Moses
Zarwanitzer, they are half-second cousins once removed.
- The
"Half" Factor: Standard second cousins share a full set of
great-grandparents. Your parents only share one great-grandfather (or
great-great-grandfather depending on the line), making them
"half" cousins. Your Relationship: You are a descendant
of a half-consanguineous marriage.
Family Tree Abbreviations
In genealogy database records, Ahnen Tafel charts, and
pedigree software, this specific connection is denoted using these
abbreviations:
- H2C1R
– Half-second cousins once removed (the direct shorthand for their
relationship)
This is the relationship that the Gedmatch listed as the
most probable from the DNA!
AI went one step further: How much genetic material do my
parents share?
- Average
Shared DNA: ~0.78%. Expected Genetic Range: 0% to 1.5%
- Estimated
Shared Centimorgans (cM): ~53 cM (with a typical statistical
distribution range between 0 cM and 100 cM).
However, my results showed 91cM, almost double the expected
amount for this connection. Largest segment = 26.7 cM. Total of segments > 7
cM = 91.1 cM.
I informed AI of my parents’ shared ancestry from the old
rabbinic lines.
“Yes, this confirms exactly where the extra shared DNA is
coming from.
Knowing that your mother's maternal side connects back to Kahana
relatives in the 1700s–1800s bridges the final gap. This historical data
directly explains the breakdown in your GEDmatch
chart. [1]
How the Kahana Connection Explains the DNA
In traditional European Jewish communities (where surnames
like Kahana and Zarwantizer are highly prominent), it was
extremely common for families to intermarry across multiple generations in the
same region. [2, 3, 4] By having Kahana ancestors on your mother's side, your
parents do not just share Moses Zarwanitzer. They also share a deeper, older
layer of Kahana/Zarwantizer ancestry further up the tree. This hidden
layout changes how your segments are interpreted:
- The
Single-Line Segment: The 26.7 cM segment on Chromosome 4 likely
stems from the more recent, direct connection—the split-wife lineage of Moses
Zarwanitzer.
- The
Deeper-Line Segments: The 21.4 cM (Chr 15) and 15.7 cM
(Chr 20) segments are very likely blocks inherited from those older
18th-century Kahana lines. Because your mother's maternal family
kept those blocks intact within their population loop, your parents both
inherited the exact same chunks.
What This Means for Your Tree
This setup is a classic example of pedigree collapse
and minor endogamy. Your tree is narrowing down as you move backward,
meaning the same individuals are filling multiple spots on your fan chart. [5]
Because of this, your parents share more genetic traits than
a standard pair of half-second cousins once removed. This historical overlap is
why their total shared DNA is inflated to 91 cM rather than sitting
closer to the statistical average of 53 cM.”
AI did not pick up on the Eiger connection here and only
based itself on the likelihood of the Kahana family ancestry. However, I have
some old charts shared to me by other researchers that show the multiple
overlaps in rabbinic families. Such as this one:
My paternal grandmother’s side and my maternal grandmother’s
side shared this common ancestor, Moses Aaron Leml Teomim-Frankel (https://www.jewgenpedia.com/families/teomim)
who passed away over 4 centuries ago!
[1] https://whoareyoumadeof.com
[2] https://encyclopedia.yivo.org
[4] https://www.familysearch.org
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