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Let me repeat: the easiest way to determine this is to look at the X chromosome. A male only has one and passes it down to all of his daughters intact. So if this woman is your half sister, you would have inherited identical X chromosomes from your father and you would match her for the full length of the X. It is the tell-tale sign of a half sister/same father relationship. I have dealt with several of these cases before. If you have significant stretches of the X chromosome NOT shared with this match, then you can't be half sisters.
Is there a way for the OP to see this and figure it out with the information she has at hand right now? or does she need to send her raw DNA and the matching cousin/sisters DNA somewhere else?
Let me repeat: the easiest way to determine this is to look at the X chromosome. A male only has one and passes it down to all of his daughters intact. So if this woman is your half sister, you would have inherited identical X chromosomes from your father and you would match her for the full length of the X. It is the tell-tale sign of a half sister/same father relationship. I have dealt with several of these cases before. If you have significant stretches of the X chromosome NOT shared with this match, then you can't be half sisters.
Thank you so much! You solved the mystery!
I just took a look at that and we share a complete half of the X but not the whole X! Thank goodness I can put that one to rest :-)
Just wondering why 23andme does not use that criteria (in addition to amount of CM's and shared DNA percent) to properly identify relationship. Maybe I will ask them why.
She is actually showing on my report as my Half Sibling.
Ancestry doesn't tell you its a half sibling, they just list it as close family. My full sibling brother (Same dad and same mom) Is in my immediate family category, while my half sister (Different dad, same mom) Shows up in my close family category.
AncestryDNA does not report a nephew as a nephew. These are the relationship categories they include:
Self/Identical Twin
Parent/Child
Immediate Family
Close Family
1st Cousin: possible range: 1st – 2nd cousins
2nd Cousin: possible range 1st – 2nd cousins
2nd Cousin: possible range 2nd – 3rd cousins
3d Cousin: possible range 3rd – 4th cousins
4th Cousin and more distant
So he is probably estimated as Close Family, and the range is probably Close Family - 1st cousin.
"A close family relationship could range from two to four degrees of separation. Close family could be an aunt or uncle, niece or nephew, great-grandparent or great-grandchild, a half-sibling, or a double-first cousin. Someone who appears in this category is rarely a first cousin."
Most companies include an estimated relationship range too, but it's really best to look at how much DNA in cMs or percentage you share rather than trying to go off the estimated relationship.
To correct your statement just a tad, great grandparent and great grandchild show up in 1st cousins category, cause my paternal grandfather, maternal grandmother, and paternal grandmother all took the ancestry test and they showed up in my close family category as well as my half sister through my mother.
I just received my DNA results back and one of matches came back showing as "Half Sibling". I have always known this person to be my first cousin (my Dad's brother's daughter). She also showed on my daughter's match as a first cousin rather than first cousin once removed.
The percent we share along with total cm's does not fall in line with first cousin or half sibling so I'm really not sure what to make of it.
This was the result with her and myself....
1365 cM
40 segments
18.3% DNA Shared
This is the result with her and my daughter.....
668 cM
25 segments
8.98% DNA shared
If someone has more knowledge about amounts and relationship I would love to have your thoughts on this!
Unless a DNA scientist is on this thread, no one here can dispute the valuation of what "half sibling" DNA is.
I just took a look at that and we share a complete half of the X but not the whole X! Thank goodness I can put that one to rest :-)
Just wondering why 23andme does not use that criteria (in addition to amount of CM's and shared DNA percent) to properly identify relationship. Maybe I will ask them why.
Thanks again Aries63 :-)
The X chromosome is only really useful for identifying a relationship at a close degree like this. With more distant matches, the X chromosome is not ideal for determining relationships because there's less recombination on it, which can fool you into thinking you're a closer relationship than you are. So most companies don't use X DNA to help determine relationships because of this. I suppose they could write it into the system to only consider X-DNA when one shares on the complete length of the chromosome, but I imagine they are trying not to over complicate things.
To correct your statement just a tad, great grandparent and great grandchild show up in 1st cousins category, cause my paternal grandfather, maternal grandmother, and paternal grandmother all took the ancestry test and they showed up in my close family category as well as my half sister through my mother.
I actually made no statement on great grandparent and great grandchild - that was quoted (copied and pasted) directly from AncestryDNA's support article I provided a link to. But people don't always come up in the exact category expected. My grandfather also comes up as Close Family, not Immediate Family like AncestryDNA expects. My point was merely that there is no category titled "Nephew" or other specific relationships like that.
Unless a DNA scientist is on this thread, no one here can dispute the valuation of what "half sibling" DNA is.
You do not need to be a scientist to know some basic things about DNA. Many of us here have been learning about these DNA tests and how they work for several years and have a good understanding of it. There are professionals who blog on these sort of topics though - not here, but we've learned a lot from them, including specific cases very similar to this one.
This kind of thing is literally what these people do for a living. If the OP has any doubt about the advice given here, she can go to any one of these professionals and get an opinion, but I guarantee they'll come to the same conclusion.
I just took a look at that and we share a complete half of the X but not the whole X! Thank goodness I can put that one to rest :-)
Just wondering why 23andme does not use that criteria (in addition to amount of CM's and shared DNA percent) to properly identify relationship. Maybe I will ask them why.
Thanks again Aries63 :-)
Just would like to clarify: when you say "we share a complete half of the X" what does that mean? Do you mean it is "half identical" and stretches the whole length of the chromosome, or you only have the right or left half in common? Because half sisters with the same father would share one entire X as a "half identical" segment in 23andMe. Females have two copies of the X, one from their father and one from their mother. A screen shot would be helpful to be sure we're talking about the same thing.
Just would like to clarify: when you say "we share a complete half of the X" what does that mean? Do you mean it is "half identical" and stretches the whole length of the chromosome, or you only have the right or left half in common? Because half sisters with the same father would share one entire X as a "half identical" segment in 23andMe. Females have two copies of the X, one from their father and one from their mother. A screen shot would be helpful to be sure we're talking about the same thing.
Sorry for the confusion....I am so new to all of this!
I meant that the line does not go all the way. It only covers part of it on the right hand side. Hoping my screenshot will come through so you can see what I meant.
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