How Much DNA Do I Share With a Great-Uncle

In this post, I will explain how much DNA you should share with a great-uncle or a great-aunt.  This is important information to know, whether you are trying to figure out how a new DNA match is related to you, or whether or not your great-aunt or uncle was a full or half-sibling to your grandparent.

But first…

What is a great-uncle or a great-aunt?

This person is a sibling of one of your grandparents. It can sometimes be confusing to use the description “great”, since we think of “great”-grandparents being one more generation removed from our grandparents. 

A great-great uncle would be the sibling of a great-grandparent, and a great-great-great uncle would be the sibling of a great-great-grandparent.  And so on, and so on.

I just wanted to make sure that we are clear on the definition of the topic of this post to avoid confusion.

What is a “half” great-aunt or “half” great-uncle?

This person would be half-sibling of one of your grandparents.  Basically, this means that your grandparent shared one parent with this sibling. 

The reason that this is important is that you will share, on average, 50% less DNA when there is a “half” relationship involved.  The reason for this is because your grandparent and this half-sibling of theirs shared 50% less DNA than full siblings do since they don’t share both parents. 

The result is that the children of these half-siblings, which would be first cousins, would share 50% less DNA than “full” first cousins.   You can probably see the pattern here.

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Will I share DNA with a great-aunt or great-uncle?

Yes!  You will always share DNA with your great-aunts or great-uncles, whether they are full or half great-aunts or uncles.  I have never heard or seen a situation where there is absolutely no DNA shared between a great-uncle and great-niece, for example.

With the knowledge that you will absolutely, always share DNA with a great-uncle, it is important to acknowledge that there is a wide range of how much DNA you will share.  You will always share some, but not always the same amount.

So, how much DNA will I share with my great-uncle?

The commonly accepted averages for a relationship of this distance are:

  • 850 centimorgans for a full great-aunt or half great-uncle
  • 425 centimorgans for a half great-aunt or half great-uncle

Sometimes, you will share a little more than the average, and sometimes a little less.  Below, you will see the average ranges for this relationship distance:

  • 575-1330 for a full great-aunt or half great-uncle
  • 215-650 for a half great-aunt or half great-uncle

Do you need to order another DNA test?

If you are trying to figure out whether your great-uncle is a half-great uncle or a full great-uncle, having other family members do a DNA test is a great way to put doubts to rest.

For example, if your grandparent or another great-aunt or uncle is available to test, you would be able to compare their DNA with that of your great-uncle. If your parent (the niece or nephew is available to test), this would also be a helpful comparison.

If you don’t have any older relatives to test, sometimes testing one of your siblings can help you determine if you are simply “low sharing” with your great-uncle.

One of your siblings might share more DNA with a great-uncle, which is very common, and this can help you determine if more research needs to be done on your recent ancestry.

You can order additional DNA tests using the links below.

The following links are sponsored links to companies that I highly recommend and have used personally:


I hope that this post helped you learn a little bit more about your DNA matches, and what to expect as far as shared DNA between you and a great-aunt or great-uncle.

Have you found someone on your DNA match list that you think might fall into this category?  Has your great-aunt or great-uncle tested?  I would love to hear from you in the comments!

Thank you so much for stopping by!

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