A DNA match for a woman has shown up on my Ancestry DNA as a second cousin with 490 cM. I recently discovered that I am thought to be the half sister of this woman's mother. My full sister shares 446 cM with the woman and my full brother shares 363 cM with her.
Could this girl be the daughter of a half sister?
Using https://dnapainter.com/tools/sharedcmv4/490 calculator I entered each of our cM values that my full siblings and I have in common with the woman.
The generated chart showed a 4.47% chance that I could be the woman's "half" aunt. I understand it to show a better chance of me being a second cousin. I also checked my sister's at 446 cM and it only showed a 1.5% chance. My brother's at 363 cM didn't show at all as a "half" uncle.
I'm really confused by all this. From what I have read, these numbers fall below the minimum of the range. My father also has 4 brothers. My father and his siblings are all deceased. My sister and I have uploaded our DNA to GEDmatch. We are hoping the woman will do the same.
Should we be able to determine the relationship through GEDmatch?
So far, Ancestry has been very accurate in predicting relationships.