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Discussion Starter #1
My FOO had issues seemingly from it's beginning. I have seen a few threads with genealogy themes so I thought I would post my scenario ....

Current understanding of blood relationships
Aunt A and Aunt Z are sisters
Niece B is Aunt A's daughter
Niece Y is Aunt Z's daughter

Geneology DNA site results say
Niece Y and Aunt A are half sisters
Niece Y and Niece B are first cousins.

We are 100% sure Niece Y and Niece B have different fathers and that their father's are men from completely outside the family.

What real life scenario could result in the geneology DNA site providing this result?
We assumed it was an error, but then I came up with what I thought might be a plausible explanation so I would wanted to tap this online community for input.
 

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DNA test was wrong? Are Aunt A and Z still showing up as sisters even though Niece Y and Aunt A are half sisters? Because that doesn't seem right, that would mean that Aunt z is also a half sister and I am assuming that didn't show up. Could the two niece fathers be brothers? Did you contaminate the test somehow?
 

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Yes that doesn't quite work. If I've got the relations right, either Niece Y and Aunt Z are also half sisters, or Aunt A and Aunt Z are half sisters. Perhaps France is right.
 

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The tests themselves, are sometimes inaccurate. Mine showed my half sister’s daughter as my first cousin, then it also said half niece. Which is more accurate. They also update which again came back the second time with my DNA reading a more accurate spread of origins.
 

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My FOO had issues seemingly from it's beginning. I have seen a few threads with genealogy themes so I thought I would post my scenario ....

Current understanding of blood relationships
Aunt A and Aunt Z are sisters
Niece B is Aunt A's daughter
Niece Y is Aunt Z's daughter

Geneology DNA site results say
Niece Y and Aunt A are half sisters
Not an expert, but don't half siblings share about 25% of genes, and aunts/nieces also 25%?
Niece Y and Niece B are first cousins.
This is what you expect, right?
 

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Discussion Starter #6
Thanks for the input so far. I suppose I should just share the theory that I desperately hope is wrong.

What if Aunt A and Aunt Z have the same birth mother "M"(which is 100% known fact), but Aunt Z's biological father is really her mother's father. How does the DNA math work if Aunt Z's father and grandfather on her mother's side are the same person, via incest between Mother M and Mother M's biological father?
Would this add enough of a DNA match to trigger a half sister connection between Aunt A and Niece Y while leaving the relationship of Niece B and Niece Y as first cousins intact? Would Aunt A and Niece Y possibly have common DNA closer to 50% than 25%?

As horrible as this sounds, if it creates a genealogical DNA probability that works then I will need to make a decision about what to do with this information. There are multiple pieces of evidence (family lore, mental illnesses and physical attributes) that would lend weight to this if it were a strong enough mathematical probability.
 

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When DNA tests are that close, the testing agency has to told of the discrepancy

Then more in depth testing needs to be done

example WW had an affair with BH's brother. if the agency is not told that the
OM was BH's brother it will show that the BH is the dad when his DNA is tested
it will do the same for the OM/brother when the normal standard test is done.

this is why the agency must be given the heads up before doing a paternity test
 

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Better ask Grandpa (Aunt A's father) some questions.

The only way that works is if he is actually also dad to Niece Y.

Aunt A's father producing offspring with her half sister (Aunt Z), would produce a child that is half sister to A, and 1st cousin to Aunt A's daughter (Niece B).

You got to hope that is an error, but it would explain it. Technically, there was no blood relationship between Aunt A's father and Aunt B, but it would be pretty wrong.
 

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Thanks for the input so far. I suppose I should just share the theory that I desperately hope is wrong.

What if Aunt A and Aunt Z have the same birth mother "M"(which is 100% known fact), but Aunt Z's biological father is really her mother's father. How does the DNA math work if Aunt Z's father and grandfather on her mother's side are the same person, via incest between Mother M and Mother M's biological father?
If A and Z have different fathers, they are going to have fewer than %50 match and their daughters B and Y aren't going to have test results that show them to be cousins, which you said they did.
Would this add enough of a DNA match to trigger a half sister connection between Aunt A and Niece Y while leaving the relationship of Niece B and Niece Y as first cousins intact? Would Aunt A and Niece Y possibly have common DNA closer to 50% than 25%?
I think a half-sibling has a match close to 25%, and so does an aunt/niece. So I think the test showed about 25%, and for some reason they only put forth the half sibling explanation, which seems dumb to me.

Why don't you contact the testing company and ask them if A and Y are just as likely aunt/niece?
 

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Better ask Grandpa (Aunt A's father) some questions.

The only way that works is if he is actually also dad to Niece Y.

Aunt A's father producing offspring with her half sister (Aunt Z), would produce a child that is half sister to A,
While A and Y share a father in your scenario, their mothers are related and so A and Y would share more genes than ordinary half siblings.
 

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Discussion Starter #12
The grandfather and the mother of Aunt A and Aunt Z have both passed, and both had a hand in their own end. Neither reached 60. Aunt Z is estranged due to untreated mental illness. I am Niece Y's uncle. She reached out to me with her concern, I shrugged it off, but continued to mull it over.
We likely won't do any deeper DNA analysis. The relationships between myself, the two aunts and our other siblings are highly dysfunctional and this pursuit would make things worse. My niece can take this on if she feels the need and I would support her.

I did find out that the grandpa died 10 months before my birth when my mother was 27. I had been told that my mother M was committed after her father died. So while pregnant with me I suppose. Another revelation in all this.
I guess this ends up being an exercise in self discovery. I grew up thinking my family was "normal" and after reading on this site for about a year and frequently raising an eyebrow when realizing I had it "worse" than many who revealed or pointed to FOO and ACE as effecting their trajectory through life I have concluded that I ran a gauntlet of traumatic events in my upbringing and I am only now starting to peel away and reveal what I had long suppressed.

I appreciate each of your responses.
 

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Just be aware that while interesting, typical genealogy testing tests only a certain set of markers and not your entire genome.

My kids for example test far closer to me than they do my wife - even though by definition their amount of DNA is 50/50. It's because I happened to contribute more of the marker sequences that they test for.

That's all this means. You might have to have more robust testing and the help of a geneticist to help you interpret the results.
 
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