Can DNA reveal if your parents are related?

Are your parents related? GEDmatch has a tool that can help you find out.


Most people might think, “my parents aren’t related,” but if you go back three or four generations you might actually find that your parents share a common great-great-grandparent.


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How can GEDmatch tell whether or not your parents are related?


You get one set of chromosomes from your dad and one set of chromosomes from your mom. If there are locations that are long enough that match on both of those chromosomes, then it’s likely that they might have inherited that from the same ancestor. These sections are called runs of homozygosity.

“Are Your Parents Related” GEDmatch evaluation criteria

The GEDmatch “Are Your Parents Related Tool” looks for an area that has at least 200 snips in a row that are the same between your two chromosomes. It’s also looking for that segment to be at least seven centimorgans long which would indicate homozygosity.


How Does This GEDmatch Tool Work?


When you log into GEDmatch. you can find the tool down in the DNA applications. The tool is called “Are your parents related?”


When you click on this tool it’s going to have you enter the kit number of a child (which can be you).


Then GEDmatch will return a map of possible homozygosity.

Map of Parents For Don’t Have Common Ancestors

In my map, there are some places with green which indicates that same for small segments but overall the tool found no indication that my parents are related.


Be Careful With The Results of “Are Your Parents Related”


Just because the tool doesn’t find a common ancestor, doesn’t mean your parents don’t have ANY common ancestor. What it means is that in the last five to seven generations, they likely do not share a common ancestor.

If you go further in time, everybody’s family tree begins to collapse in on itself.

If you want to learn more about “runs of homozygosity,” you can actually go to David Pikes' website (https://www.math.mun.ca/~dapike/FF23utils/ ) and read some more about it. Be warned, the information is rather technical. If you are not into this technical aspect of DNA, then this website is probably not going to interest you

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Which Kits Can I Use This Tool With?


This tool runs really fast and it is something that you can do on every single kit now.

If you know that you are adopted, then this might be good to do to find out whether or not you have parents that share common ancestry.

If you are part of an endogenous population, I would highly encourage that you run this tool. You are most likely going to find that there are a lot of places that you actually had DNA inherited from both parents.

Looking at Someone With Parents Who Have Common Ancestors


Here is what someone that actually has parents with common ancestry, as found with this tool.

DNA of someone whose parents are related

You can see that it looks a lot different than what mine did. It still has mostly red but there are some bigger sections of green all interspersed within. In those big sections, the segments have also been highlighted blue underneath indicating that these are a match they meet that threshold of 200 snips and of seven centimorgans.


As you examine this person’s chromosomes, you can see on several of the chromosomes there are these runs of homozygosity. At the bottom of the report, we can see that the largest segment was actually $30 emergence.


That’s actually a really large segment. There’s a total of 242 centimorgans that are part of these runs of homozygosity.


You can see an estimate of the number of generations in which this occurs. There are about four generations between one parent and the other parent. That’s perhaps the great-great-grandparents. So, these parents might share a set of great-great-grandparents or great-great-great-grandparents in common.


Try Out The “Are Your Parents Related” GEDmatch Tool


I encourage everybody to actually use this tool. It’s one of the first things that you should do. It is a quick tool that doesn’t take too long. For most people, the “Are Your Parents Related” tool will come up with not being related in the last several generations. For those of you who do have recent common ancestors, then you have a clue of what you might find as you’re searching your family tree.


We have a video series dissing how to use the different tools on the Genesis system on the GEDmatch website. Click here for that playlist


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