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FTDNA’s “in common with” feature

Those of us who, like The Legal Genealogist, have tested our autosomal DNA with Family Tree DNA’s Family Finder test often come up against that common question:

What to do when a DNA match uses a feature at the website that allows that match to select a “known relationship” with you, and you don’t know anything that will confirm it. This came up again just this week in a Facebook discussion among genealogists.1

Now, just so we’re all on the same page, this particular feature only exists with the Family Finder test, which is offered only by Family Tree DNA and which tests only autosomal DNA — the kind of DNA test that works across genders to locate relatives — cousins — from all parts of your family tree.2

The range of possible known relationships for the Family Finder test is as broad as the range of relationships in families: all the way from parent-child at the near end to distant cousin on the far end. But the ones that appear in your results page give you a relationship range and then a suggested relationship, like these two from my most recent set of matches:


Notice that there’s also a column on the right called Known Relationship, with a button you or your match can click on to assign a specific relationship. That triggers a notice to the other person that a known relationship has been selected, and you can see all the pending notices if you choose the Known Relationship drop-down box from the Family Finder menu at the top of the results page:


So when you get a notice that says someone has selected a known relationship as, say, a third cousin, and you have absolutely no idea what your relationship to your match might be, what should you do?

The answer, realistically, is: nothing.

Because the odds are, the request isn’t being made because the match does know the relationship between you; it’s being made because the match doesn’t know it.

And because selecting a known relationship, even where one isn’t known, activates one of the most useful features of the Family Finder interface — the “in common with” feature.

You see, you can look at your Family Finder matches in lots of different ways, filtering them to see, for example, only those who are very closely related to you or who share a common surname. And one of the options you can choose is the In Common With filter:


If you choose that option, then in the box underneath that option you will have another drop-down list of matches:


Choosing a name from that list of matches will present you with a filtered list of people who match both you and the person whose name you’ve selected. So I can, for example, see only the people who match both me and my half-brother, to quickly and easily isolate those of my matches who’ll be on our shared paternal side, eliminating all those on my mother’s side.

Or I can choose my Fore cousin and identify people who’d be the best to contact to try to work on that line, in which my cousin and I share a set of third great grandparents.

Or I can choose my grandmother’s cousin whose most-recent-common-ancestor with me is the Shew-Battles line — her great grandparents and my 3rd great grandparents — and isolate only those likely to share that lineage.

It’s an absolutely wonderful tool when you want to work on one segment of your DNA matches at a time and essential to making sense of your results.

But here’s the kicker: the only matches who will appear in that list are matches where you have gone ahead and assigned a known relationship.

Now you don’t need to actually know a relationship to assign one. You can, for example, just select the suggested relationship or use distant cousin as a generic kind of label. You can — you should! — write yourself a note using the notes feature reminding yourself that you’ve chosen a relationship for analysis purposes only:


But selecting any relationship there for a match where you really don’t know much about the match lets you see who else in your match list that particular match also is related to. Here, for example, is a match of mine named Robert, and you can see the first three of my other matches in the in common with list:


Pretty clear that I’m going to be looking on my mother’s Cottrell side and not my father’s Geissler side, isn’t it? And if we continued to look down the list, we’d see that Robert matches a number of my other matches who share one surname from one area of North Carolina as well. Which tells me even more precisely where Robert and I should look to find our common ancestors.

The key here is that Robert doesn’t have to confirm the relationship for me to be able to use this feature. And I wouldn’t need to confirm it for him to be able to use it if he’d assigned it at his end.

So what should you do when a DNA match uses a feature at the website that allows that match to select a “known relationship” with you, and you don’t know anything that will confirm it?


… Or everything you can to learn enough to confirm it!


  1. Yolanda Campbell Lifter, status update, 2 Aug 2013, Facebook ( : accessed 3 Aug 2013).
  2. See generally Judy G. Russell, “Autosomal DNA testing,” National Genealogical Society Magazine, October-December 2011, 38-43.
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