Shared Matches of Matches | How SMOM Help DNA Discoveries

Diahan Southard

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Shared matches of matches are game-changing for genetic genealogy. We’ll explain how these work with your DNA match list and where to find the tool at MyHeritage DNA, 23andMe and now at AncestryDNA.

When five people take the same class, they may each learn—and contribute—something a little different, based on their different perspectives.

When learning about your DNA matches, the same thing happens with the Shared Matches of Matches tool (SMOM). It offers you an insightful perspective on how your matches are related to each other. This knowledge can help you more easily sort out the common ancestor that your matches share and therefore help you more quickly discover your relationship.

Why Shared Matches of Matches matter

SMOM is available at three of our DNA testing companies: 23andMe, AncestryDNA, and MyHeritage DNA. No matter which company you are at, you will want to click on one match of interest–let’s call them a Best Mystery Match–and then review how much DNA that match shares with your shared matches.

What are you looking for with Shared Matches of Matches?

Simply put: you are looking for large discrepancies between the amount of DNA you share with a particular person, and how much your Best Mystery Match shares with that person. 

As a very general rule, anyone sharing over 400 cM with your Best Mystery Match is very closely related to them, and therefore you could likely figure out their connection. Identifying their connection with each other will help you better isolate the line in their family tree that connects you.

Here’s an example

Let’s say you have a Best Mystery Match named Ademir, with whom you share 72 cM. This amount is enough to make you and Ademir third cousins. That means you could share any one of Ademir’s EIGHT 2X great grandparent couples. Identifying which ancestral couple you share could be very difficult to figure out if you don’t have more information.

However, with SMOM you see that while you are only sharing 64 cM with another match named Bruna, Ademir is sharing a whopping 847 cM with her! That means that they could be first cousins to each other. And sure enough, when you compare their trees, you can see that they are first cousins on Ademir’s dad’s side. Now with that one extra piece of information, you know that you are likely also related to Ademir on his dad’s side through one of the four paternal 2X great grandparent couples. 

Looking at one more shared match, Vos, you see that Vos shares 243 cM with Ademir, but only 58 cM with you. When you compare their trees, you see that Vos shares a 2X great grandparent couple with Ademir. This tells you that you are very likely related to these three people through this dark blue couple in Ademir’s tree.

Therefore, one of the first steps you should take when investigating your relationship to a Best Mystery Match is to check their shared matches list and look for matches who share significantly more DNA with them then they do with you.

How do you access the Shared Matches of Matches tool?

23andMe: Relatives in Common

Choose a DNA match, then scroll down past your genetic relationship, family background, ancestry and haplogroup comparisons. When you get to the Relatives in Common list, click the big button for finding relatives in common. 

The first column lists the matches you have in common. The second column shows you how much DNA you share with each of these matches, reported in a percentage (rather than actual shared cM), and an estimate of your genealogical relationship. The third column shows you how much DNA your match shares with each of these people. 

Unfortunately, you can’t re-sort your match’s column to see the ones they’re most closely related to. You just have to scroll down and look for their closer relatives, like JB, who is your match’s son, and the next listed match, who is your match’s daughter.

AncestryDNA: Shared Matches of Matches

This feature is available to those who have subscribed to Ancestry Pro Tools. You’ll find it on your match’s profile page, as an option next to where you can click to view their trees or ethnicity (see below).

As shown below, a list of the matches you share with this match appears in the left column. Your shared DNA is reported in the middle column, and the match’s shared DNA with them in the right column. Across the top of the chart you’ll see tools for sorting and filtering this list. (Alas, at this time of writing, you can’t sort by the match’s closest matches.)

MyHeritage DNA: Shared DNA Matches

Under the DNA matches tab, click on any match. Scroll down until you see your Shared DNA Matches list. Mine is shown below. For each of these shared matches (who appear in the middle), I can easily compare how much DNA I share with them (on the left) with how much my selected match shares with them (on the right). Better yet, if I sort by the amount of shared DNA with my selected match (where the red arrow is), the top of the list on the right will show their closest matches that we share. Now I can see that this match’s daughter has tested, along with other close relatives. I can use that information to help build this match’s tree toward my own.

Just as a reminder, the genealogical relationships shown here and below are estimates based on how much DNA you share. There’s always more than one way you can be related, so you need to do the research to confirm the actual genealogical relationship.

Now that you’re finding all these matches–and learning so much more–wouldn’t it be better to communicate more effectively with them? Yes. Yes, it would be.

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<a href="" target="_self">Diahan Southard</a>

Diahan Southard

As founder and CEO of Your DNA Guide, Diahan Southard has been teaching people how to find family history answers in their DNA for several years, and she's been in the genetic genealogy field since its infancy. Diahan teaches internationally, writes for popular magazines, consults with leading testing companies, is author of Your DNA Guide–The Book, and producer of Your DNA Guide–the Academy, an online learning experience.


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