How Much DNA Do You Share With a Great-Grandparent?

How much DNA do you share with a great-grandparent? Will they show up on your DNA match list? In this post, find the answers to these questions and more!

More people have tested their DNA than ever before. This trend, combined with people living longer than ever, as well as increased access to technology for those who are younger (and older!), has led to DNA matches across multiple generations.

For example, we now see DNA results that include everyone from a child to a great-grandchild, and everyone in between. This does sometimes invite questions, however.

Below, I will answer some of the most common questions relating to DNA shared with a great-grandmother or great-grandfather.

How much DNA do you inherit from your great-grandparents?

We have inherited an average of 12.5%, of our DNA from each of our grandparents. The actual amount inherited from any of our eight great-grandparents will vary, and could range from as low as about 4% to as much as 23%

In centimorgans, the unit of measurement used to determine genetic distance, we can expect to have inherited an average of about 930 cMs from any of our great-grandparents. However, there is a normal range (as noted above) which means that someone could inherit as few as as about 300 cMs and as many as about 1700 cMs.

Will you always share DNA with a great-grandparent?

Yes, you will always share DNA with all of your great-grandparents. This is because your grandparents each inherited half of their DNA from their parents, who are your great-grandparents.

While it’s true that we don’t share DNA with all of our relatives, and didn’t inherit DNA from every single ancestor in our family tree, we are too closely related to our great-grandparents to have not inherited DNA from them. So, you will always share at least some DNA with all eight of your great-grandparents.

How does great-grandparent show up on DNA results?

If you are lucky enough to have a living great-grandparent, or even more than one, you might want them to take a DNA test. Alternatively, you might have a DNA match that could be a great-grandparent.

Your great-grandparent will show up as a close relative on your DNA match list. Exactly how they are displayed, and the category that they fall into, will depend on the company that you have chosen to use for DNA testing.

For example, on Ancestry, DNA matches are sorted into a few different categories: Parent/Child, Full Sibling, Close Family, Extended Family, and Distant Family. Most people will find that their great-grandparents show up in the Close Family category.

Below, you can see an example of a great-grandchild to great-grandparent (specifically, great-grandmother) match on Ancestry DNA. It is from my adult daughter’s DNA match list, and since I have also tested my DNA with Ancestry, it tells my daughter which side of the family this match is on:

As you can see, my daughter shares 785 cMs with her great-grandmother. This is equal to about 11% of her total DNA, slightly under the 12.5% average amount.

How to know if your DNA match is a great grandparent or another relative

As you know, there is a range of shared DNA that we typically see between great-grandchildren and their great-grandparents. The range, with the average of about 930 cMs, happens to overlap the ranges of shared DNA for many other relationships.

Since a great-grandparent is a close relative, it would be very important to determine whether a DNA match is indeed related in this manner. There are several other close relatives whose ranges of shared DNA overlap with the great-grandparent relationship:

• Half-aunt or half-uncle
• First cousin
• Half-niece or half-nephew
• Half-sibling (over 1300 cMs shared)
• Full niece or nephew (over 1300 cMs shared)
• Full aunt or uncle (over 1300 cMs shared)
• Grandchild or grandparent (typically over 1300 cMs shared)

If you and your DNA match share on the lower end of the range (i.e. much less than 930 cMs), then there is a much broader list of relationships that you might have. For example, first cousins twice-removed can share over 400 centimorgans, which overlaps with the low end of the range of great-grandparents/great-grandchildren.

If you have a DNA match that you believe could be a great-grandparent, there are a few things that you could do in order to determine whether you are – or aren’t – related to this DNA match in that way.

For example, if you believe that your match might be a great-grandparent, they should share much more DNA with your parent, or their siblings. If you have a grandparent (who you believe to be descended from your great-grandparent) able to take a test, they would show up as a Parent/Child match.

You can use your age, and the age of your DNA match, to eliminate further possibilities. A great-grandparent must be significantly older than you, your parents, and your grandparents, for instance.

Furthermore, you can research other DNA matches that you and your potential great-grandparent match share in common. If your match shares matches with you who are related to both of your grandparents, for example, this could mean that your match is descended from your grandparents, and is not the parent of one of them.

Conclusion

Thanks for sticking around until the end of this article. I hope that you learned exactly how much DNA you share with a great-grandparent, how they will show up on your DNA match list, and how to know whether your match is a great-grandparent or someone else.

If you have any questions about something that you read in this post, or if you would like to share a specific question about shared DNA with a great-grandparent, I would love to hear from you in the discussion below.

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