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Can DNA Matches Be False?

Are you wondering if DNA matches can be false? What is the probability that your DNA match is false? In this post, I’ll answer these questions – and more!

Questions addressed in this article include:

  • Can DNA matches be wrong?
  • Are close DNA matches ever wrong?
  • What are the odds that a DNA match is false?
  • Which company has the most accurate DNA matches?
Can DNA Matches Be False_

It’s important to know whether a DNA match is false. Have you ever spent hours trying to figure out how you are related to distant DNA match, only to eventually figure out that you probably aren’t really even related?

I have, and I want to save you some time.

Can DNA matches be wrong?

Yes, it is possible for distant DNA matches to be false. It is most common to have false DNA matches that share a single segment that is smaller than 10 centimorgans (cMs) in length.

It is important to note that a legitimate DNA match can also appear to be false based on not finding genealogical evidence of a connection.

DNA segments can get passed down for many, many generations. Many times, we might be related to DNA matches that appear to be false, but neither person has a family tree that is complete (or accurate) enough to be able to provide definitive proof that there is (or isn’t) a connection.

Or maybe you ARE related, but the link is maybe 16 generations back in your family tree – too far back to ever find the common ancestor?

If you have a false DNA match, it doesn’t mean that the testing company made a mistake. Instead, the DNA that you share with your DNA match is “coincidentally” identical.

The technical term for coincidentally identical DNA segments is identical-by-state. These segments are different than DNA segments that are identical because of common descent (identical-by-descent).

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False positive DNA matches: What are the odds?

As I mentioned before, the odds that a DNA match is a false match increases with smaller DNA segments. This means that there is a low probability, or even almost zero probability, that larger segments are false.

For example:

  • Segments over 15% have a 0% chance of being false (i.e. not inherited from mother or father)

Most segments between 10-15 cM are legitimate segments, inherited from a common ancestor. This common ancestor may be too far back to identify, however.

With smaller segments, we can see the odds of the match being false increase dramatically:

  • Segments under 10 cM have about a 15% chance of being false (i.e. not inherited from mother or father)
  • Segments under 5 cM have about an 85% chance of being false

Most experts in the genetic genealogy field recommend only focusing serious research on matches that share at least one segment that is larger than 10 cM in length. Just about every person who has done a DNA test should have many matches that match at this threshold, which should provide sufficient work and entertainment.

Close DNA matches are never false

I’m going to make a pretty bold statement:

Close DNA matches are basically never false.

DNA matches that are estimated to be related to us at a third cousin level or closer are most definitely related to us in some way. DNA testing companies use the amount of shared DNA that we have with our matches in order to estimate our relationship with our match.

You can use information like your family tree along with shared DNA to figure out the most likely connection with your match. This post can help you understand shared centimorgans and how to learn how you are related to your DNA matches:

The only exception to my “bold” general statement applies to people with substantial ancestry from endogamous populations, like Native American, French-Canadian, or Ashkenazi Jewish. DNA matches that fall into this category are not “false” matches, but are likely much more distantly related to you than is estimated.

If you think this might be the case with your “close” DNA matches, you can read this post:

How to know if you have false DNA matches

Have you ever heard someone say that it’s impossible to prove a negative?

When it comes to DNA segments, it’s very difficult to “prove” beyond doubt that there is no common ancestor at some point in history shared between two individuals.

Since when we talk about false DNA matches, we are referring to people who share only one or two very small DNA segments with us, it is unlikely that we can ever find compelling evidence to show that it is impossible that we are related.

Additionally, many of these smaller segments are impossible to trace. This means we can’t find compelling positive evidence of a connection.

How many of us have accurate, DNA verified family trees that go back 15-20 generations on all lines? No one has a tree like this, because it isn’t possible to verify DNA going back this many generations.

Which company has the most accurate DNA matches?

One of the most common questions that I receive in my inbox is whether it is possible to have false matches on Ancestry DNA. Others inquire as to which company provides the most accurate DNA matches.

The odds of finding false positive matches is just about the same on any DNA testing website. I think I get more e-mails about Ancestry DNA only because it’s the most popular DNA testing company.

This means that Ancestry DNA matches are just as accurate as matches that you will find on My Heritage, and vice versa. You won’t get more accurate matches on 23andMe than you will on Family Tree DNA.

The only slight difference that you will find across DNA testing companies is the “threshold” used to determine whether a person will show up on your list.

For example, some companies will only show you people who share with you segments that are longer than 10 cM. Other companies will show you people who only share 6 cM.

Still others might show you people who share as low as 4 cM with you as long as the total number of centimorgans shared reaches a different threshold.

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I hope that this post has helped you understand more about false DNA matches, how common they are, and how to spot false DNA matches in your match list.

If you have any questions about something that you read in this post, or if you would like to share your own experience finding a false DNA match in your list, I would love for you to join us in the discussion below.

Thanks for stopping by today!

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Carole Young

Sunday 31st of January 2021

Hi Mercedes

Is it possible that I could have a false NEGATIVE result? My alleged half siblings and I were tested by easy DNA and the results are negative. The samples were sent from two different countries. There is no other explanation, that we can find, for us not to be related. Any information on this process would be appreciated. Carole


Monday 1st of February 2021

Hi Carole, I would suggest that both of you test with either 23andMe or Ancestry DNA in order to see how much DNA you share. That's the best way for you to figure this out. I hope that this helps, Mercedes


Tuesday 19th of January 2021

Hi Mercedes.

Does the dna get split(mother/father)in the laboratory for testing? My results (23andme)show my mother is Scandinavian and that is extremely accurate since I have complete ancestry charts. The results for my father show he is British/Irish when everyone in our family knew him to be Jewish. If the dna does not get split, then I'm OK with the unexpected result. If the dna does get split, then the lab seems to have made a huge error.

Thanks for you reply, Ross.


Wednesday 20th of January 2021

@Mercedes, thanks again for your reply ~ much appreciated! My parents are dead, so won't be able to go that route, although my brother's DNA test confirms that my "father" is his father. I did take another DNA test with ancestry and am awaiting the results. Yep, thanks for the luck wishes - should be interesting to see if my Mom's greatest secret is revealed. And then, if it's real - I get to try and find out WHO is my real father. All the best, Ross.


Wednesday 20th of January 2021

Hi Ross, The DNA testing companies do not separate or split your DNA for ethnicity estimate purposes. Depending on which company testing your DNA, and whether either (or both) of your parents have done DNA tests with the same company, you may be able to view phased DNA matches, which essentially separates DNA matches out by maternal vs. paternal lines. You could learn more about your recent ancestry, including your father's lines, by studying your closest DNA matches to see which ancestors they share in common with each other. I wish you the best of luck in solving the mystery of these unexpected results. Sincerely, Mercedes


Sunday 13th of September 2020

I have a DNA match of 1709 cM across 46 segments what is our relationship and can it be wrong?


Tuesday 15th of September 2020

Hi Mike, It is unlikely to be incorrect, especially if the rest of your DNA matches are what you might expect. This person is likely a fairly close relative (i.e. a half-sibling, aunt/uncle, niece/nephew, or grandparent/grandchild). You can narrow down the relationship possibilities using age and geographic information, as well as comparing your family trees. I hope this helps! Sincerely, Mercedes


Wednesday 9th of September 2020

I am adopted, so after 2 years of no close DNA matches, this week I was very excited when the below match was posted. It indicated that this person is either my first cousin or great niece. It should be noted I am 97% Ashkenazi Jew. Shared DNA - 12.7(889.4 cM) Shared Segments 24 Largest segment - 82.4cM I was in touch with this young lady and we concluded that I could be related to her mom via our biological Dad. Her Mom was adopted as well. Yet, while I match this young ladies DNA, I did not match any of her Mom’s DNA. We were thinking her Mom and I were half sisters via our Dad who is an Ashkenazi Jew. Could I have a half sister and not share any of her DNA? We exchanged pictures and her Mom’s eyes and mouth look similar to mine. Moreover, we are both petite in stature.

Any insight you can give me, I would really appreciate it! The DNA site used was MyHeritage. Thanks, Ally

Jeff Faircloth

Thursday 13th of August 2020

I feel pretty confident that a friend and I are closely related, at least first cousins and perhaps even half brothers, but we are not even showing up as related at all (matched) on Family Tree DNA. Is this even possible or are we definitively and absolutely not related at all? Thanks!



Friday 14th of August 2020

Hi Jeff, Thank you for your question, and I am sorry that your results are not showing what you expected to see. Did you both just recently get your results back? Sometimes it can take a few days for matches to "populate" on some of the testing sites. You could also consider uploading your DNA to Gedmatch (along with your friend) to compare it with the One-to-One Autosomal tool. First cousins and half-brothers share a sizeable amount of DNA, so it would definitely show up if you are related in this way. Sincerely, Mercedes

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