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Track DNA Matches You Can’t Place In Your Tree

Do you have DNA matches that you can’t place in your family tree? In this post, find tips that will show you how to find the extra information you need to figure out where they fall in your tree.

Track DNA Matches You Can't Place In Your Tree

DNA matches are very useful for learning about your ancestors, where they may have lived, and building your family tree. However, you can only use them for this if you are able to figure out how you are related.

In other words, you want to figure out who the common ancestor is that you share with your DNA match.

It can be very frustrating to spend time working out your relationship with a DNA match with no avail. Maybe your match doesn’t have a very big family tree – or any family tree.

Fortunately, there are a few things that you can do to find new information that can lead you to your shared ancestor.

I’ll take you through these tips while using one of my mother’s mystery DNA matches as an example.

Estimate distance of MRCA

The first thing you should do is use your amount of shared DNA to estimate how far back you need to look in your respective family trees to find your most recent common ancestor (MRCA). It is important to know where your shared ancestor should be in your tree.

Small segments mean distant common ancestors

For example, if you share only one small DNA segment of 17 centimorgans (cMs), you should know that your common ancestor could be 8 or more generations back in your family tree. While it would be possible for a closer relative, such as a third cousin, to share a low number of centimorgans with you, it is more likely that this is a distant cousin.

With distant relatives sharing only one small DNA segment, we should consider that the MRCA could be more than 8-10 generations back in our tree. The common ancestor could be much further back than a 6th great-grandfather (i.e. a great-great-great-great-great-great grandfather), which in my family tree takes me back to the early 1700s.

Most of us do not have complete, accurate family trees going back to the early 1700s on all lines of our trees, and this does explain why we are not able to easily identify the ancestor that we share with many of our more distant DNA matches.

More shared DNA means closer common ancestor

You may have closer DNA matches that you can’t place in your tree, with whom you share a larger amount of DNA. This would mean that if you both had family trees, you should only have to look back a few generations in your family trees to find your common ancestor.

My mother has a DNA match that I was not able to learn much about until I did a bit of research for this article. She shares 346 cMs with this female DNA match.

If I plug 346 cMs into this calculator, I see that there is a 100% chance that my mom and her cousin are related at a distance of second cousin once-removed or closer.

This means that I don’t need to look any further back than great-great grandparents for both my mother and her DNA match to find their most recent common ancestor. This is a good clue because it eliminates a lot of time-consuming searching.

Determine which line of your tree you are related through

You can eliminate many potential shared ancestors by trying to learn which side of your family you are related through. This is a method that works best with closer cousins, and doesn’t work as well with very distant cousins.

Mom or dad’s side?

The easiest way to narrow down a potential ancestor that you might share with your DNA match is to figure out if the match is paternal or maternal. If you tested with Ancestry and have a subscription, you can do this automatically – the matches are sorted for you by Parent 1 or Parent 2.

You can also use your shared matches, or matches that you share in common with your match, to figure out which side of your family your match is on.

Hopefully, you have a DNA match on both sides of the family that is fairly closely related, such as a first cousin. If the first cousin also shares your target DNA match in common with you, then they are likely related to you through ancestors of the grandparents that you share in common with your known first cousin.

Specific lines of your family tree

If you have more distant cousins, such as known second and third cousins, on your DNA match list, you can use sharing these matches in common with your target match as a clue that you might be related through ancestors of your great-grandparents and great-great grandparents that you share in common with those known relatives.

When I examined my mother’s mystery DNA match for shared matches, I immediately realized that this DNA match is related on my mother’s German lines because she shares all of my mother’s DNA matches from that line of her tree in common.

Shared matches might have better family trees

Sometimes, we can solve our mystery immediately upon looking at matches that we share in common with our DNA match. Some of these matches might have more complete family trees, and even share a surname with our DNA match.

If you check through the family trees of the closest DNA matches that you both share in common, you might be able to find a pattern that shows the group of matches has a common shared ancestor. This could be your ancestor, too, or the ancestor that is shared in common with the group could be an ancestor that you have in your family tree.

When I was looking through the DNA matches shared with my mother’s mystery match that I mentioned earlier in the post, I realized that they have a relative in common who shares less DNA with my mother, 113 cMs, but has the same uncommon last name as my mom’s DNA match.

I took a look at this person’s family tree and realized that, sure enough, the match-in-common is descended from two sets of my mother’s great-great grandparents. This means that my mother is related to them twice because my mother is related to both their great-grandfather and their great-grandmother.

A quick obituary search confirmed that my mother’s mystery DNA match (346 cMs) is the mother of the match that they share in common. The mother is my mother’s first cousin twice-removed, the grandchild of their common ancestor, and the daughter (133 cMs) is my mother’s second cousin twice-removed.

My mother shares more DNA with these two DNA matches than she typically would because she is related to them in more than one way. They have four most recent common ancestors instead of the typical two.

Of course, I made sure to add these two new DNA matches and their ancestors on the collateral line of my family tree to my tree on Ancestry to help me keep things straight. This is an important part of building a wide family tree.

Look for common ancestral geographic areas

If you have access to a family tree built by your cousin, and you know a bit about your family history, you might be able to identify geographic areas that both of your families share in common. This could be a clue about your shared ancestors, and it is an important step if you didn’t find any clues while examining shared matches.

For example, if you are in the US and have ancestry in North America going back to colonial days on your dad’s side of the family, and post-1890s European immigrant ancestry on your mom’s side, you might already know that a lot of immigrants settled in the New York City and Newark areas upon arrival.

If you have a DNA match that has a few generations of their tree built with ancestors living in Newark or New York City, you could consider the possibility that your DNA match is related on a line of your tree connected to your recent immigrant ancestors.

Try building out lines of their tree

If your DNA match has a small family tree linked to their profile or results, you might be able to find your shared ancestor by building out a few lines of their family tree. This works best if you already estimated your relationship and have a geographic focus in mind before you start.

You might already have a theory about how you are related based on your shared matches, and by building out a line or two of their tree using your research skills, you may be able to identify your connection this way.

I do this very frequently, as once you get a lot of practice with genealogy records, it can be pretty easy to use sites like Ancestry or Family Search to quickly find the parents of someone’s ancestors and add a few generations to their tree. I write it down on a piece of paper – nothing fancy.

If you have the data, try chromosome mapping

If you are very determined to figure out how a match is related, and you have the available data, you might consider a method called chromosome mapping. Chromosome mapping assigns segments of your chromosomes to specific ancestors through identifying ancestors shared with DNA matches with whom you have identified your connection.

Once you have mapped a significant portion of your chromosomes, you can plug in data from new matches and see if the DNA segments that you share with the new match overlaps with segments that have already been assigned an ancestor.

The easiest way to do this is on a site called DNA Painter.

In order to use chromosome mapping, whether it is on DNA Painter or a spreadsheet, you must have access to detailed data about the location of DNA segments that you share with your match. This is not available from sites like Ancestry, and this information is sometimes restricted on other sites, so chromosome mapping is a long-term project that requires patience and diligence.

False match is a possibility

If you have endlessly traced possible connections with your DNA match and have found no clues, and you share a single DNA segment that is smaller than 15 cMs in length, you should consider the possibility that you are not really related to this DNA match.

It is possible that you and your DNA match are false matches.

Consider an NPE scenario

If you have explored all of the ideas in this post, yet you don’t think you are false matches, and you have read my checklist about how a match could be related, and you still can’t find a connection, you could consider the possibility that one or both of you have a NPE scenario in your family tree.

This would mean that either you or your DNA match has a line of their tree that does not contain biological relatives. In other words, a non-paternity event may have occurred and paternity was assigned to the wrong person.


I hope that this post about tracking connections with DNA matches that you can’t exactly place in your tree has been helpful. If you have any questions about something specific that you read here, please let me know in the discussion below.

Thanks for reading today!

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