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My sisters, two aunts and several cousins (on maternal side) did the 23 and me DNA test. One of my aunts (the younger one) showed up as a half sister to me (we share 1,942 cM and 44 segments) and my sisters; and as a full sister with my other aunt.

Does this indicate that she could be a child of incest between my mother and my grandfather?

Is further testing available to determine if this is true or not?

  • With my other aunt I share 1971 cM and 48 segments.
  • My two aunts share 2804 held identical cM and 47 segments, 977 cM and 41 completely identical.
  • My sisters and I share as follows:
    • myself and oldest 2768 cM and 47 segments half identical and 1004 cM and 35 segments completely identical.
    • Myself and middle one 2865 cM and 43 segments half, 984 cM 38 segments completely identical.
    • My two sisters: Half identical 2797 cM 49 segments, Completely identical 1052 cM 37 segments.

I also have numbers for my aunt I question and her daughter. My grandmother supposedly had 8 kids.

The aunt in question is 5 years older than my oldest sister, and they had a younger brother as well. The reason we are suspect is that it was known that my grandfather molested his daughters.

You were correct on suggesting one of the links. We are uploading file to GEDmatch (www.gedmatch.com)and using the “Are our parents related (AYPR). test. That should answer our question.

I’m not sure if the test answered my question. The AYPR test from GEDmatch resulted in “your parents are probably distantly related” - Largest segment = 9.6 cM. Total of segments > 7 cM = 18.7 cM. For the other aunt it stated no evidence parents are related.

I ran david pike's runs of homozygosity - www.math.mun.ca , but I don’t understand the results.

PolyGeo
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user11097
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  • https://genealogy.stackexchange.com/q/9296/19 may be worth reviewing. – PolyGeo Feb 07 '20 at 00:38
  • https://genetics.thetech.org/ask-a-geneticist/identifying-incest-dna may be worth reviewing – PolyGeo Feb 07 '20 at 00:39
  • I empathize with your situation and desire to find an answer to your question. I’m no expert on analyzing relationships like this so will probably leave my answer as-is for now, to see if someone else answers, or whether I can find time to look into the additional details. – PolyGeo Feb 07 '20 at 21:13

1 Answers1

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The Shared cM Project 3.0 tool v4 suggests these relationship probabilities for 1,942 cM (based on stats from The DNA Geek):

  • 100.00% Grandparent Aunt / Uncle Half Sibling Niece / Nephew Grandchild
  • ~ 0% ** Great-Aunt / Uncle Great-Niece / Nephew

** this set of relationships is just within the threshold for 1942cM, but has a zero probability in thednageek's table of probabilities

This match looks like it supports your aunt being your aunt, but half sibling also seems possible if your younger aunt is not much older than you, and I would need to know the match values of the other relationships in order to comment further.

PolyGeo
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