In this post, I’ll help you understand the basics of the “predicted relationship” on Ancestry DNA. You will learn what the term means and how to use this information.
Whether you are just starting out learning how to understand your DNA match list, or you have a specific DNA match in mind that you’d like to try to understand, you have come to the right place.
- How Ancestry DNA determines the predicted relationship
- Whether the predicted relationship is usually “right”
- How you can use the predicted relationship and other information to figure out how you are really related to your match
The predicted relationship is a very important clue about how our DNA matches might be related to us. Understand how we are connected to our DNA matches is the best way to learn more about our ancestors from our DNA results.
How does Ancestry DNA determine the predicted relationship to a DNA match?
In order to determine exactly how you might be related to someone, Ancestry compares your DNA to the DNA of your potential relative to see how much genetic material you share. This shared DNA is measured in “centimorgans“.
Simply put, centimorgans are used to measure genetic distance on a matching DNA segment (i.e. a “piece” of DNA that matches another piece of DNA that your that your relative has).
We generally share more numerous and longer DNA segments with closer relatives, and shorter and fewer DNA segments with more distant relatives.
It’s possible to share dozens of DNA segments with a DNA match, and it’s also possible to share only one DNA segment with a match. Generally speaking, the longer the longest shared segment, the more recent the common ancestor.
While there is no hard and fast rule as to exactly how much DNA people with any given genealogical relationship (i.e. how you are related in your family tree) will share, there are clear patterns. There are generally accepted ranges of shared DNA for many of the most common relationships.
What do I mean by a range of shared DNA? Let’s examine first cousins. Full first cousins, where both people share two grandparents, 575-1330 centmorgans (cMs) of DNA.
Simple enough, right? Not so fast!
People who shared between 575-1330 cMs of DNA could also be half-aunts or half-uncles, or even a great-grandparent or great-grandchild.
Are predicted relationships on Ancestry usually “right”?
As you might have guessed by now, there is really no right or wrong when it comes to the relationship prediction. Since the relationship prediction is based on the amount of shared DNA, and except for the very closest relationships (such as a parent/child connection), there are at least a few different relationships that can fall within any given range.
Sometimes, there are several relationships – or even many, many potential relationship types that could fall within the range for any given relationship category.
In other words, the predicted relationship is only an estimate. It can’t really be wrong or right.
When you are looking at a particular category of relationship and you notice that Ancestry has predicted that you might be related to a cousin in a particular way, it is important to understand that it is only an educated prediction. It is not necessarily evidence that you are actually related in that way.
Sometimes, a person who is predicted to be your first cousin will actually be a first cousin. Other times, they might be slightly more closely related, or slightly more distantly related.
So, what does “predicted relationship” on my DNA match list really mean?
The predicted relationship on your Ancestry DNA match list does serve a purpose. Even if you know that the relationship that is predicted isn’t 100% fact, it is helpful to have a general idea about how you may be related to someone.
Even if sometimes it is a very general idea.
For example, if you have a DNA match who is predicted to be related to you at a 5th-8th cousin relationship distance, you can feel confident that this person is not your first or second cousin.
Conversely, if you have a person who is predicted to be related to you at a 1st-2nd cousin level, then you can feel confident that they are not distantly related to you. These examples are extreme, but helpful.
We have to do the “hard” work to figure out the nuance in between relationship possibilities. Our families aren’t set up neatly with only first, second, and third cousin categories.
Someone could be a first cousin twice-removed, or a second cousin once-removed, or even a half-second cousin twice-removed. As well all know, families are complicated.
How to know how you really might be related to a match on Ancestry DNA
In order to know how you are really related to a person on your DNA match list, you’ll need to know how to access the exact number of shared centimorgans (cMs).
Once you have this information, you can use Blaine Bettinger’s chart available in my post “Beginner’s Guide to Shared Centimorgans” to figure out the relationship possibilities that exist for that amount of shared DNA.
If both you and your DNA match have posted your family trees, it should be easy to know where to look to figure out your relationship. If you don’t, it’s still possible – keep reading!
After you’ve determined the relationship possibilities for a given DNA match, you can then use more traditional methods to work out your genealogical relationship.
Learning the following information about your DNA can help you eliminate relationship possibilities and know exactly where to look to find more information about how you and your match are connected:
- How old is your match (obviously, a person who is younger than you can’t be a grandparent or a great-grandparent!)
- Where does your match live? Where were they born? Were any of your family members born there, too? Did anyone in your family tree live in the same town?
- For very close matches, comparing your “ethnicity” estimate with that of your match could possibly help you figure out which regions you share in common, and potentially which ancestor – this is not a foolproof method, however, but it can give you something to work with
- Have you contacted your match to see what they know about their family? See tips on contacting DNA matches
I hope that this post has helped you the basics about how Ancestry predicts how your DNA matches may be related to you, what exactly predicted relationship means, and how you can really find out how you are related to your DNA match.
If you have any questions about something that you read in this post, I’d love to hear from you in the discussion below.
Thanks for stopping by!
Monday 12th of December 2022
A recent DNA match showed a Fran as a 1st or 2nd cousin. We share 1029 cM and 15% shared DNA. By our reckoning, Fran is the daughter of our great uncle (my mother's uncle). However, I have two other 1st cousins (verified because I know them) who are children of my father's sisters and brothers. Both of these 1st cousins share fewer cMs (973 and 878) and a lower percentage of shared DNA (14% and 13%). How could I have more of a connection with the child of a great uncle (my mother's uncle) than to children of my father's siblings?
Thursday 8th of October 2020
is it possible to share 3400 cMs over 38 segments with someone and not be related? I don't know the person but my DNA identified match insists that I am not his father.
Friday 9th of October 2020
Hi Douglas, 3400 cMs is a very high number of centimorgans to share with a match. This is about 50% of our DNA, so we would expect a DNA match sharing at this level to be either a parent or child (since we get 50% of our DNA from our parents and pass 50% of our DNA down to our children). If the rest of your DNA matches are what you might expect (i.e. you have 1st, 2nd, and 3rd cousins descended from known ancestors), then you can exclude the possibility of a mistake in testing, which is extremely rare but possible. If you feel like your results are correct, you might be interested in reading this post: https://whoareyoumadeof.com/blog/what-to-do-if-you-get-a-surprise-dna-match/ If you tested on Ancestry DNA, you might also refer to this page: https://support.ancestry.com/s/article/Unexpected-DNA-Matches