What is an Eighth Cousin?

Are you interested to know what an eighth cousin is and whether you are genetically related to them? In this article, we'll help you understand what an eight cousin is, whether they are considered family, and what DNA results might say.

You have likely heard of first or second cousins but have you ever heard of eighth cousins? Some may not realize that technically for each generation of ancestors we have, we also have another set of cousins. The further the generation separation from us the higher the cousin level number.

So, what are eighth cousins? How are we related to them?

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What is an Eighth Cousin?

Eighth cousins are recorded in our family tree in a couple of alternate ways such as 8th cousin or 8C for those looking to abbreviate. So how are they related to us? Well, it's really quite a simple explanation, an eighth cousin is someone who has the same great-great-great-great-great-great-great grandparents as us. In order to save time going forward in this post, we will just refer to these ancestors as 7th great grandparents.

So let's explain this in a little more detail. Our 7th great grandparents possibly had several children one of which was our 6th great grandparent. The brother or sister of that 6th great grandparent would be the 6th great grandparent of your 8th cousin. Essentially you share a set of common ancestors with your 8th cousin.

How Closely Are Eighth Cousins Related to Us?

First, let's start by creating some perspective when it comes to the closeness of familial relationships. Our close relatives include grandparents, parents, aunt/uncles, siblings, children and grandchildren. They are essentially the closest members of your family who you likely see on a regular basis.

Extended family is the next level of family and these include cousins up to and including our third cousins. They are the family who we see less frequently and in some cases not at all. I personally have several first cousins who until a few years ago I did not know or have contact with.

So now we come to the distant family, these are those who, although they are related to us, we very likely do not know and probably will not knowingly meet in person. Once we reach the fourth cousin level and beyond these family members are considered technically distant relatives. Interestingly I do interact frequently with one of my fourth cousins on Facebook, a person I discovered through my dive into my family history.

So then an eighth cousin, a person with whom we share our 7th great grandparents, is very much in the distant cousin category. Unlike first and second cousins we are highly unlikely to know an eighth cousin by name and certainly would not have knowingly met them.

This distance however does not mean that we have never met an 8th cousin just that we likely did not even know we had done so. If your family has remained in the same area for generations it is highly likely that you have multiple 8th cousins living in the same region. You could be standing behind one at the store or sitting next to one at the movies. In fact, in some cases, you could be married to one.

How Many 8th Cousins Do We Have?

I hope you are sitting down while reading this post because the answer to this question may come as a surprise. We first have to consider this important point of fact, each generation we go back in our family the number of direct ancestors we have doubles exponentially. Well actually there is a point in which pedigree collapse becomes a factor but that is for another time and another post.

Cousin Level Estimated Number of Cousins
First Cousin 5
Second Cousin 28
Third Cousin 175
Fourth Cousin 1,570
Fifth Cousin 17,300
Sixth Cousin 174,000
Seventh Cousin ?

As the table above shows we should in theory have 512 different 7th great grandparents. Two of these distant grandparents would be the couple that you and your seventh cousins descend from.

If we consider those 512 7th great grandparents as 256 couples who have had offspring who themselves had family we start to realize something. There are eight generations of people having children who are either directly related to us or are related as cousins.

Imagine that your 7th great grandparents had 5 children who each had 5 children of their own. This would produce 25 grandchildren for your 7th great grandparents. If those 25 grandchildren all had an average of 5 children that would be 125 great-grandchildren. You may be able to see where I am going with this.

In my search for a statistic for how many 8th cousins we may have, I was only able to find estimates as far as 6th cousins. However, this should still illustrate the magnitude of how many 8th cousins we might have.

Cousin Level Estimated Number of Cousins
First Cousin 5
Second Cousin 28
Third Cousin 175
Fourth Cousin 1,570
Fifth Cousin 17,300
Sixth Cousin 174,000
Seventh Cousin ?

As the table indicates at a rough estimate we might have 174,000 6th cousins. With each generation, the number of cousins grows as does the multiplication factor. Seventh cousins could be in the low millions which could put eighth cousins in the tens of millions.

Allow that to sink in for a second and consider that New York City has a population of roughly 8.8 million people. Your eighth cousins could potentially fill that city twice over.

This all assumes that every child in every generation lives to adulthood and has children of their own and that no pedigree collapse occurs. The truth is that realistically it wouldn’t be in the hundreds of millions. We simply can’t say how many ninth cousins we have.

Are Eighth Cousins Related by DNA?

This is a good question because as we have already mentioned 8th cousins are considered distant relatives. Well, let me first say that beginning at 3rd cousins we start to find that we have individuals who, while they are clearly related to us via blood, we actually do not share common DNA with.

Due to DNA recombination, each generation we are separated from our common ancestors increases the likelihood that we might not share DNA with our cousins from our generation. This is not to say we do not share DNA with any of our 8th cousins, merely that the amount may be very small.

The truth, however, is that we likely only share a small amount of DNA with a tiny fraction of our millions of 8th cousins. This does not mean we are not related because as long as we are direct descendants of the same ancestors we are still family.

Other Eighth Cousin Types

There are some other terms that might apply to the 8th cousin based on slightly different relationships.

Eighth Cousin Once Removed

An 8th cousin once removed would be the parent or child of your 8th cousin. This term once removed essentially means that they are a cousin just from a different generation. They are a generation closer or further away from your shared ancestors. If they are two generations closer or further away then they would be twice removed.

Half Eighth Cousin

This is an easy relationship term; it essentially means that the children of your 7th great grandparents from whom you and your 8th cousin respectively descend were only half-siblings. This meant they only had one common parent and therefore you descend from only one of your 7th great grandparents, not two.

Conclusion

Our eighth cousins are distant blood relatives with whom we share common ancestors. There are potentially millions of 8th cousins out in the world. We could work with them, shop at the same stores or even be married to one and not even know it.

We likely do not share DNA with the vast majority of them but we are still family by virtue of those mutual ancestors.

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  • "What is an Eighth Cousin?". NameCensus.com. Accessed on May 17, 2022. http://namecensus.com/blog/what-is-an-eighth-cousin/.

  • "What is an Eighth Cousin?". NameCensus.com, http://namecensus.com/blog/what-is-an-eighth-cousin/. Accessed 17 May, 2022

  • What is an Eighth Cousin?. NameCensus.com. Retrieved from http://namecensus.com/blog/what-is-an-eighth-cousin/.