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How to Use DNA Matches for Genealogy

In this post, you will learn about DNA matches and genealogy, and specifically how a beginner can leverage the knowledge gained from a DNA match list to build a family tree.

Everyone says that doing a DNA test is the best thing that you can do if you are interested in genealogy and family tree research, and it’s true – it is extremely helpful.  If you’ve done a DNA test, however, you might be overwhelmed with your DNA match list. 

How to Use DNA Matches for Genealogy

Before you really delve into your research, you should clear your mind of preconceived notions and expectations about your family tree.  DNA is a fascinating journey; you never know where it will take you and who you might find on your way. 

Instead of using your DNA matches to prove that the work that you’ve done on your family tree is correct, I encourage people to use what they already have as a guide. However, we should be willing to explore alternatives if their DNA matches lead them in a different direction.

Below, you will read the steps that you should take when using DNA matches to build your tree.  Obviously, it’s easier if you already know a little bit about your family history, but you should still be able to use your DNA matches to find your biological family if you are adopted, or don’t know one of your biological parents. 

(Read here for a story about how I helped a family member find her father’s biological family using her DNA).

Get as many DNA matches as you can

In order to effectively use your DNA matches for genealogy, the first step is to get access to as many DNA matches as you can. A higher number of DNA matches will allow you to learn as much as possible about your ancestors and your family tree.

The goal here is to fish in the biggest pool of DNA matches possible.  You never know which company your DNA relatives used to do a test, so you want to have access to as many sites as possible. 

Additionally, many people who do DNA tests don’t upload or include their family trees on their profile.  By having the largest amount of DNA matches possible, you will be able to view the family trees of your matches and learn as much as possible.

No matter which company you tested with, you should download your DNA and upload it to the following sites:

Some important thoughts on transferring DNA in order to get the most from your test results:

  • If you are just getting started and haven’t tested your DNA yet, I recommend doing your test with Ancestry DNA.  They have the biggest database, and then you can just download your data and upload it for free to the sites I mentioned above – you get the most for your money and lots of great matches!)
  • If you already tested, but you tested with Family Tree DNA to begin with, don’t worry.  You can still upload your DNA to the other three sites.  Ancestry DNA and 23andMe don’t accept transfers from other companies.
  • If you tested with Ancestry DNA, upload to the other companies for free, and then, if possible, do an additional test with 23 and Me.

Once you have a nice variety of close and distant DNA matches to help you with your research, you can then move on to the next steps.

Click here to buy the Understand Your DNA Results Ebook

Organize your DNA matches into groups of their likely relationship to you

You will now want to try to organize your DNA matches into groups:

  • First cousins
  • Second cousins
  • Third cousins

(Learn about my journal for organizing DNA matches)

I will deal with fourth cousins and more distant cousins separately in a different section – don’t worry!  Distant cousin matches are often quite interesting and helpful.

The relationship estimates that the DNA testing companies give you are simply estimates.  They use the amount of shared DNA to determine how you might be related, but for each relationship type, there is typically a range of average shared DNA. 

Most of these ranges overlap with ranges of other relationship distances.  In order to determine an exact relationship, you’ll have to learn more about your matches (i.e. view their family trees, or contact them to learn what they know about their family).

How to figure out how your top DNA matches are related

If you don’t have a very extensive family tree, and don’t know much about your family’s origin, the DNA matches that will be most useful to building your tree will be towards the top of your list. 

A key number in deciding how someone is related to you (or how they might be related to you) is by checking to see how many centimorgans you share with your match.  (Read this post to learn how to check how many centimorgans you share on Ancestry). On Family Tree DNA and My Heritage DNA, shared centimorgans are clearly displayed.

This chart will help you determine how closer family matches are related to you:

Centimorgan Chart for Close Family Relationships

Place your cousins into family groups

Once you’ve “collected” all of your cousin, and figured out your approximate relationship to them, you should then determine which matches are related to each other. 

The idea is to divide them, or place them, into family groups.  There are a few ways to determine how DNA matches in family groups are related:

  • Common surnames in their family tree
  • The same people in their family tree
  • Shared matches (on Ancestry DNA), Matches in common (FTDNA), or “People who match one of both of two kits” (Gedmatch)
  • Identical geographic locations

Note:  Sometimes, more than one sibling or other family member from the same immediate family will do a DNA test.  Obviously, everyone from this same family will share the same common ancestors, so just watch out for this and don’t place too much emphasis on the shared common ancestors if you see this situation.

Decide whether the common ancestors match what you know about your family tree

Once you’ve spent a lot of time working with, and looking at, your various DNA match lists, you will have a pretty good idea of whether what you’ve learned matches what you know about your family history. 

If everything matches what you already knew, then you can feel very confident using your more distant cousin matches to build your family tree back even further.

If you find a cousin or two that doesn’t seem to fit into your family

If you have a first, second, or third cousin match that doesn’t seem to fit anywhere in your family, especially if they have a family tree that doesn’t match yours, and you have determined that your tree is correct, it is possible that you have stumbled upon a non-paternity event – either in your family or theirs. 

This simply means that, a few generations back, there could be mis-attributed paternity (or even maternity). This is also sometimes called a non-paternity event.

What’s a non-paternity event?  It is sometimes abbreviated as a NPE, and it means that, basically, the father who is in the family tree really isn’t the father. 

Or the mother.  There are so many reasons, like informal adoptions, which were much more common in certain countries or several generations ago in the US.

If you believe that you have stumbled upon a NPE in someone else’s tree, my recommendation is that you don’t do anything about it. 

It doesn’t directly affect what you know about your family history, so unless someone specifically asks you to help them with their tree and wants you to tell them everything you’ve found, I would just keep the information to myself.

An example of finding a NPE among DNA matches

I actually have had this situation come up in my own research more than once.  There were always rumors that one of my grandmother’s brothers was a half-brother. 

I thought that they were just that – rumors.  The siblings and cousins grew apart, but no one thought that the rumored half-brother had had any children (the brother has long since passed). 

I determined that there would be no way to prove the rumor correct or incorrect.

One day, I had a new cousin match show up on Ancestry DNA.   I took a look at the tree and immediately spotted the common surname and ancestors. 

This person is the granddaughter of my grandmother’s brother – a first cousin once-removed to my mother.  The only problem was that Ancestry DNA placed this cousin in the 3rd cousin category to my mother. 

They only share 167 cMs – lower than people at this relationship typically share if they have a “full” relationship.  Their shared DNA is perfect for being half-first cousins once-removed, however.

The rumor is now verified.

I won’t say anything to my new cousin match unless she asks me, however.  My family tree remains unchanged by this knowledge, and it isn’t my place to make someone else feel unsure about who their grandfather’s father was.

What if you find many DNA matches that don’t fit into your tree?

Like many, many matches that don’t fit into one or both sides of your tree?  And no matches that fit into your family tree as you know it?  

Or only matches that fit into your immediate family, but not the family of your parents, grandparents and/or great-grandparents?  You might have accidentally stumbled upon a NPE or adoption situation without knowing it. 

It’s possible that a parent, grandparent, or even a great-grandparent was adopted and either it was a secret at the time, or the knowledge about it has been forgotten.

What do you do if you find out something like this?  I always recommend building a true and correct tree – since that is why we all do this whole genealogy thing. 

Use the information that you have learned about the common ancestors to try to figure out who your real ancestors are on that line.  Should you tell your family members? 

I usually recommend that, unless specifically asked, you keep information to yourself , especially if it will cause more pain that gain for your family.  Again – unless specifically asked.

Use your 4th cousins and beyond to build your family tree out even further

The process for using 4th cousins and more distant to build your tree is similar to that of the closer family – but unless you are extremely interested or have lots of time on your hand, you probably won’t want to put them all into a spreadsheet (though you can!).

The average person has:

  • 940 fourth cousins (you’ll share genetic material with about 430 of them)
  • 4700 fifth cousins (you’ll share genetic material with about 700 of them)
  • 23000 sixth cousins (you’ll share genetic material with about 1320 of them)

The most helpful thing to look for among 4th cousin and more distant matches are common surnames.  You have thousands of cousins, some of whom might be as interested, or more interested in family research – and some of them might have discovered important information about your common ancestors. 

I would definitely encourage you to search for 4th cousins and beyond who have family trees and share common surnames with you.  This will help you build your family tree even further out.

Some of your fourth cousin (and even distant) matches will actually be more closely related that the software algorithm predicts.  As I mentioned above, there are ranges of shared DNA that are common among different relationship types, and some of those ranges are very low at the bottom of the range. 

I recommend searching through distant cousin matches to find some of those “closer” relatives that just happen to share very low amounts of DNA with you, since this doesn’t really affect how you are related genealogically-speaking.

Read more about when distant cousins aren’t really distant.

How to learn even more about your family history

The best way to learn as much as you can using DNA is to have your older family members do a DNA test, as well.  Your mother, family, aunt, uncle, grandmother or grandfather, or even great-grandparent, will have different ethnicity estimates, and different DNA matches – though many will be similar. 

If your relatives take a DNA test for ancestry and share their results with you, their DNA match list can be used with the same strategies that I mentioned in this article. If your relative is your parent, full aunt, uncle, grandparent, or full-sibling, their ancestors are also your ancestors, which means that their DNA relatives are also related to you.

You will also be able to figure out any discrepancies that you have found in your research, since the amounts of shared DNA will be able to help you narrow down some of your theories about your ancestry.

Learn more about why it is good to test older relatives


I hope that this article has helped you learn a little bit about how you might use your DNA matches for the purpose of genealogy.  I would love to hear your stories and answer your questions – please feel encouraged to leave a comment.

Thank you for stopping by!

Share the knowledge!

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Monday 2nd of May 2022

Thank you for this article. It was really helpful and informative. I will need to refer to it again to fully understand all of the points you have made.

Di Shawn J. Gandy

Sunday 22nd of August 2021

Hello Mercedes,

I love this article. It's so informative, and instructive to research I'm doing now in helping a friend who is adopted find her biological parents.

You said you left your tree unchanged when the rumor of one of your grandmother's brothers being a half sibling was confirmed. I had a similar situation and I went back to my tree and disconnected my 2nd great-grandfather as the biological father of that particular sibling g of my Great Grandfather because they had two different dads. Should I not have done that?


Friday 27th of August 2021

Hi Di Shawn! Thank you so much for your question and your comments. I decided to leave my tree unchanged because my grandmother still has a living sibling, and because everyone else from the next generation is still alive and I did not want to cause anyone distress. DNA testing has revealed many family secrets on both sides of my family, and there have been other times with more distant ancestors (like 2nd great-grandparents) that I have made changes to my public tree. In your case, you are probably fine, but you know your family best. I hope that this helps! Sincerely, Mercedes

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