I am a female. Another female and I have come up as sharing 1915 cM's and when we do the one to one X-DNA on GED Match, if we click on "prevent hard breaks", we have a straight blue line across the bottom, and all yellow and green across the top (primarily green). We also get this info: Largest segment = 190.1 cM Total segments = 190.1 cM (100.052 Pct) 1 shared segments found for this comparison. 19820 SNPs used for this comparison.

Are we correct in concluding that we are half sisters?

We both know who our Mother's are. We share DNA with others on Ancestry and GED Match.


The Shared cM Project 3.0 tool v4 suggests for 1,915 cM that the relationship has these probabilities (based on stats from The DNA Geek):

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

and that the:

[second] set of relationships is just within the threshold for 1,915cM, but has a zero probability in thednageek's table of probabilities

Assuming that you are from the same generation as your match then half-sisters seems likely. If you think there is a chance that you come from different generations then you could consider the other possibilities.

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  • We were born 3 months apart and we both know who our Mothers were. We have similar matches with both of her paternal grandparents. Our story is even more complicated, but I was just wanting confirmation on reading the X-DNA GED Match graphics. So, again, thank you. – JoGe Jan 25 at 4:58
  • Hopefully someone familiar with X-DNA testing can provide an answer to complement mine. – PolyGeo Jan 25 at 6:22

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