Same Parents, Different Ancestry? Ethnicity Results Explained

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Is it possible for two siblings to have the same parents, but have different ethnicity results?  This question sometimes causes people to panic, wondering if they have uncovered a family secret. 

Is it possible that two full siblings who have the same two parents show different ancestry?

The resounding answer is YES.  This is totally possible, and in fact, probably.  If you have checked the amount of shared centimorgans, and determined that you and your brother/sister are full siblings, this post will help you understand how and why your ethnicity results look different.

In order to assist with my explanation, I have two examples from actual Ancestry DNA results that should help illustrate how this can happen.  All of the people used in my two examples are verified full siblings, and show the usual amount of shared DNA for that relationship category.

Note:  Some people might wonder if the ethnicity results come back different on two full siblings, does it mean that the Ancestry DNA results are not accurate? 

In truth, the opposite is true!  Ancestry DNA results are very accurate.  They are so accurate that they are able to pick up on the subtle differences between the DNA that each sibling inherited from each parent.  More on this below 🙂

When Two Siblings Share Different Percentages of the Same Ethnicity

Sometimes siblings share all of the same ethnicities, but show very different percentages.  In the graphic below, you can see that Frank and Julie both have Ireland, Europe West, Great Britain, Scandinavia, and the Iberian Peninsula in their ethnicity estimates, but all of the percentages are different.

They even show small amounts of West Asia DNA, but in different amounts.  How odd, you might think.  (Are you thinking that?)  These are 100% full siblings – how can the same parents, different ancestry happen?

Why Siblings Show Different Ethnicity Percentages

When two people have children, each child inherits 50% of their DNA from each parent.  As far as scientists have been able to tell, the process is fairly random. 

While each sibling gets 50% of their DNA from each parent, they don’t get exactly the same selection of DNA as their siblings.  You might see where I am going with this story.

Imagine that that both of your parents have a refillable basket full of DNA, and you have your eyes closed.  You reach in and grab half of the DNA from each basket – what you would have left is your full genome (your unique collection of DNA). 

Then, along comes your sister.  She reaches into the basket, too, with her eyes closed.  Some of the DNA that your sister grabs will match yours, but some won’t.

Since you both had your eyes closed, you won’t have chosen all of the same DNA!  Just like in real life, when you were conceived, you got a random selection 50% of each parents’ DNA.

So how does ethnicity come into play in this example?  In the example above, Frank and Julie both reached in and grabbed some DNA that matched all of the same ethnicities, but they randomly grabbed different amounts of each one. 

For example, Frank grabbed more DNA from his parents that matched Ireland than Julie did.  And Julie grabbed more Scandinavian DNA that did Frank.

Something important to note:  Even if Frank and Julie’s parents had lots of kids, there will always be some DNA that none of their kids “grabbed” out of the basket.  The reason that this is important is because there could be some of that DNA “left behind” that doesn’t get passed down, and there could be unknown ethnicities contained within those genes.

When a Sibling Shows an Ethnicity That the Other Doesn’t Have

This is where it gets really interesting, and sometimes even exciting.  The image below is the ethnicity results for three full siblings.  They all share more than 50% Eastern European, and a nice percentage of DNA from Great Britain, but there are some ethnicities that show up in one that don’t show up in the others.

See it for yourself:

If Nicole had been the only sibling to test her DNA, she would have gone on about her life thinking that her parents were basically just Eastern European and British.  She would never have known about the Irish, which showed up in Sarah’s test. 

And wow, look how different Mark’s results are!  Where did those African and Asian results come from?

Mark, Nicole, and Sarah all wish that their parents could have been alive to do one of these genetic genealogy DNA tests.  I imagine that there would have been slightly higher percentages of African and Asian in at least one of the parent’s results. 

There could even be some other trace ethnicities that these three children did not inherit.

Since these siblings can’t test their parents, they are glad that they have all gotten together and done this test and “recreated” the most complete version of what their parents’ ethnicities might have been that is currently available.

The best way to get this complete picture of your family’s ancestry is to test your siblings and/or parents.  If you are interested in purchasing an additional DNA test for a relative, please consider using the following link.

An added bonus?  The DNA that each sibling inherits that the other siblings didn’t inherit will also provide additional DNA matches.  This is a fantastic way to find 3rd-8th cousins that don’t match you, but can help you research your ancestry.

Conclusion

I hope that this explanation has helped you understand how you and your siblings can be full siblings (i.e. you share both parents) and have different ethnicity estimates from your DNA test.

Did you find anything curious when you and your siblings did the test?  I’d love to hear your story in the comments!

Thanks for stopping by!

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