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.
