Are you curious about the number of DNA matches that you have, and why it doesn’t exactly match the number that your parents have?
If both of your parents have also tested their DNA, you might wonder why you don’t match all of the people that they do. You might even have DNA matches that they don’t have, which truly doesn’t seem possible.
You might have noticed that both your mother and father have DNA matches that you don’t have – and it might not make a lot of sense. If both you and your parent are related to someone, shouldn’t they show up on your DNA match list, too?
In this post, you will learn:
- Why you won’t have all of the same DNA matches that your parents have
- Why you might have DNA matches that your neither of your parents have
Why don’t have all of the same DNA matches that my parents do?
There are a few different reasons that cause us to have different DNA matches than our parents do. Some companies, for example, such as 23andMe, have a maximum number of DNA matches that they show us on our lists.
The most common reason we have different DNA matches than our parents is more complicated.
What led me to write this article was something that occurred to me this morning, when I was looking at my own DNA results on My Heritage DNA. When you manage more than one DNA kit on My Heritage, you can see a summary of all of the DNA tests that are on your account right from your main DNA page.
This is what I saw this morning:
The first thing question that came to mind was this: If my dad has 1068 DNA matches, and my mom has 2190 DNA matches, why don’t I have 3798 DNA matches on my list?
As you can see, I only have have 2269 DNA matches. What is the meaning of this?
Am I not related to all of those other DNA matches that are on my mother and father’s list?
The answer is fairly simple: Yes, I am related to all of the people who my mother and father are related to – in a genealogical sense. If someone is related to my father, for example, I am also related to them.
We share a common ancestor, and share a branch, if you will, of our family tree. The matter gets complicated when you introduce DNA, however. We can share an ancestor with someone, and truly, legitimately, be related to them, and yet have no genetic connection.
I inherited 50% of my DNA from each parent to make up my full genome. What this also means is that I only inherited 50% of each parents’ DNA.
There was 50% of the DNA of each parent that I didn’t inherit. So the primary reason that my dad and my mom have DNA matches that I don’t have is because I didn’t inherit the DNA segments that match those individuals. My parents still have all of their DNA, and so the DNA test is still able to match those segments together.
It’s usually as simple as that, really.
Our shared DNA segment might be too small to show us as a match
Every DNA testing company has a “threshold” for the minimum size of DNA segments needed to show that two people are matches. While the minimum segment varies by company, it typically ranges from 6-8 cMs (centimorgans).
So, another reason that I don’t see some of my parents’ DNA matches on my list is that I may have inherited only a small portion of the DNA segment that my parent shared with the match. This smaller DNA segment might fall below the required threshold that my DNA testing company has set in order to show people as DNA matches.
If my dad shared 20 cMs with the match across one DNA segment, I may have inherited a segment from my him that matches on only 5 cMs. This would cause the person to not show up as a DNA match for me, even though we are related.
Why do I have DNA matches that neither of my parents have
This is a less common question, but it’s still important to address. There are three reasons that you might show DNA matches on your match list that don’t match either of your parents.
It’s a temporary glitch
It’s very uncommon, but it is still a possibility that there is a temporary bug in the software causing DNA matches not to fully display. I’ve noticed this on occasion.
Sometimes, if neither of my parents show up as a shared match, I will see them still on my parents’ match lists. It’s just a fluke and no further attention should be paid to it.
You are not really related to the DNA match
Almost always, if neither of our parents match a DNA match, this means that we are not related to the DNA match. In these cases, it means that the DNA segment that we share with the false match is an coincidentally identical segment and not due to a shared ancestor.
It is possible to have a DNA segment that is “coincidentally” identical, also known as “identical-by-state“. In the genetic genealogy world, this is called “identical by state”, meaning that it just randomly happens to be identical.
This is most likely to happen with very small DNA segments (less than 5 cM in length), but can happen every once in a while with a larger segment (there is only about a 1% chance that a 11 cM segment is coincidentally identical). It’s rare to have this occur with segments larger than 15 cM, and it would also be statistically improbable to have more than one identical by state segment larger than 5 cM with the same match.
You could be related on both sides of the family
It’s possible to be related to someone on both sides of your family, and this can “skew” your total amount of shared DNA.
You can be related to someone in more than one way, and sometimes, if you are only distantly related on both sides, it’s possible that the segments that your parents share fall below the matching threshold set by your testing company, but when you have them together, like you do, it shows up as a match.
This would only happen with really small segments, which occur with pretty distant relatives.
There are all sorts of wild scenarios in the DNA world, as you can see.
Conclusion
I hope that this post has helped you understand a bit more about how DNA is inherited, why your parents will show different numbers of DNA matches and match people that you don’t. If you have any questions, concerns, or just want to share your story, please feel free to leave me a comment below.
Thanks for stopping by!