My half-sister and I recently completed DNA tests with myHeritage.com. The results don't show us having matching DNA. We share the same father.

Is it possible that we are half siblings even though there is no DNA match?


4 Answers 4


If you are really half-sibling, and you took the test from correct people, you WILL have a shared DNA. A half-siblings share ~25% of DNA between each other. Or 1300-2300 cM.

The chances that the examples were accidentally mixed in laboratory are very small.


In a prior answer it was stated that you would share between 1200 and 2300 cM of DNA. This is the primary way to validate if you are true half-siblings.

But, you might also want to compare your close matches with the matches that your tested half-sibling shares. Do both of you have matches that are the same DNA donors? If so, you might want to pursue those matches and see how you are related to them (who are your common ancestors). If you don't share any similar matches then it's even more probable that you are not half-siblings.


Yes it's possible - assuming you are both female you will share an entire x chromosone which ancestry and my heritage do not test for - but gedmatch.com does. It's possible to not share any autosomal DNA with a half sibling as hereditary of the same chromosones from a a parent varies even with full siblings. Upload your DNA data on gedmatch if you are sisters and compare you x DNA...of course won't work between male/female siblings. I am curious though if you went that route what did you learn? Are you siblings (I'm going through this right now too)

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    You are completely wrong about this. To quote from the correct answer "half-siblings share ~25% of DNA between each other. Or 1300-2300 cM."
    – user6485
    Jul 27, 2018 at 17:55

I have read an article from a DNA scientist that said there is a 1 in 10,000,000 chance for FULL SIBLINGS to NOT MATCH at ALL on Autosomal DNA. No known case has been known to exist, as would be very hard to detect anyway, as would need both parents DNA in first place to confirm. How could this occur in theory, by each sibling having the exact OPPOSITE DAD/MOM section of the DNA-for all regions of the DNA. I would imagine the ODDS for Half Siblings are less than the 1 in 10,000,000. For cousins-ever lower-but again-pretty much impossible to ever identify or confirm. Someday, with all the DNA now on file, a known case may someday surface-but will be super rare-like winning lotto-but some do win. All this being said, it is HIGHLY unlikely to be anyone's answer to a non match. One would need both parents DNA to test, then both Siblings. So, I'm not suggesting this is someones answer, but just to point out, just when you think you know all the answers there may be some rare exceptions.

Also, chimerism can cause some odd DNA readings as well as 'Double Cousin".

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    Hi, Welcome to G&FH.SE! I have down-voted your answer because it is low quality. First of all, suppose someone wanted to read the article you cited. Your reference to the article is too vague to be of use. Your answer could be improved by 1) putting your statement that the answer contains edge cases at the very top and 2) including a concise list of cases with links to relevant articles. Your answer could also be improved by less use of upper case.
    – Jan Murphy
    Dec 21, 2019 at 19:10

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