After taking an AncestryDNA test, I matched a half brother, who I'll refer to as Y to preserve privacy, and sister, who I'll refer to as X. Both appear to come from the maternal side (both adopted and all family information verifies a male and female child).

My results now show that my full sister, who I'll refer to as S (and I grew up with) is actually my half sibling. I share no paternal DNA with her, but share maternal DNA. We all have the same mother.

However, my half-brother Y and half-sister X do not show my (assumed) full-sister S as a DNA match. A transplant surgeon verified that I am half sister to each of them.

What in the world is going on here?

Why don't Y and X appear as a DNA match to S?

We are confident we all share the same mother. Mother has passed and no idea who the father could be.

  • 1
    Hi, Kim, I have closed your question temporarily so we can improve it. First of all, if you took an AncestryDNA test, that was an autosomalDNA test, not mitochondrial. When you say "A transplant surgeon verified that I am half sister to each of them." was that as a result of testing for something like a kidney transplant (tests not taken at Ancestry)? How have you determined what side of the family the DNA matches are?
    – Jan Murphy
    Apr 21, 2018 at 21:14
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    I've redacted the names of your (half) siblings because including them appears to contravene our Privacy Policy - see genealogy.meta.stackexchange.com/q/3337/19
    – PolyGeo
    Apr 22, 2018 at 1:11
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    @PolyGeo I've tweaked your name substitutions to improve readability.
    – Jan Murphy
    Apr 22, 2018 at 22:11
  • That works fine for me @JanMurphy
    – PolyGeo
    Apr 22, 2018 at 22:44
  • If we have inadvertently changed the crux of your question with our edits please feel free to re-clarify them using the edit button beneath your question. Please make every effort to preserve the privacy of your siblings here even if they do not mind you waiving it because our site is not set up to record any acceptance of that waiving.
    – PolyGeo
    Apr 23, 2018 at 1:32

1 Answer 1


Are you saying that X and Y don't match S genetically at all? Or are you saying that X and Y aren't a good match for S in terms of organ transplant? Because those are two totally separate things; any two siblings, even full siblings, can have very different HLA types for organ and/or stem cell transplants.

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