Skip to Content

What is an Eighth Cousin?

Do you want to know what an eighth cousin is? In this post, learn the definition of an eighth cousin, as well as lots of other interesting eighth cousin facts.

Along with learning about exactly how eighth cousins are related, you will discover:

  • Whether eighth cousins are distant cousins
  • What an eighth cousin once-removed really is
  • The definition of a half-eighth cousin
  • How many eighth cousins you have
  • Whether eighth cousins are blood related

In other words, you will learn just about everything you want to know about eighth cousins.

What is an Eighth Cousin

These are very distant cousins, yet they can be very helpful in learning about your family tree. Even so, it can be a bit confusing to try to understand exactly how eighth cousins are connected.

We also have a substantial number of eighth cousins. So, let’s get started figuring out where all of these cousins fit into our family tree.

What is the definition of a eighth cousin?

An eighth cousin, also written as 8th cousin, is someone who shares great-great-great-great-great-great-great grandparents with you and is descended from a different child of those 7th great-grandparents.

The most recent common ancestor shared between eighth cousins is a 7th great-grandparent.

In other words, your great-great-great-great-great-great grandparents (6th great-grandparents) and the great-great-great-great-great-great (6th great-grandparents) of your 8th cousin were siblings.

Confusing, right? Those are a lot of greats, which is one reason why some people prefer to write 6th or 7th great-grandparents when talking about eighth cousins.

It saves both time and space.

Tip: If you and your cousin share your 6th great-grandparent as a common ancestor, then you might be seventh cousins.

What is a eighth cousin once-removed?

An eighth cousin once-removed is a child of your eighth cousin. Alternatively, it could be the parent of your ninth cousin.

8th cousins once-removed share as a MRCA (most recent common ancestor) 7th great-grandparents, since we count back to the MRCA beginning from the relative who is closest in number of generations to the common ancestor.

We sometimes see 8th cousins once-removed abbreviated as follows: 8C 1R.

Related: What is a Cousin Once-removed?

Are eighth cousins distant cousins?

Eighth cousins are very distant cousins. In fact, most people don’t consider eighth cousins a significant family relationship because we have so many of them.

Generally speaking, we consider cousins who are related at a distance greater than third cousins to be distant cousins.

How many degrees of separation are there between 8th cousins?

There are eighteen degrees of separation between 8th cousins. This is a large number of degrees of separation compared to first cousins, for example, who have only four degrees of consanguinity between them.

In order to calculate the degrees of separation between eighth cousins, we count up from ourselves to our common ancestor, the 7th great-grandparents, and then down the generations to our 8th cousin.

If you try this, you will find that you must count nine generations back to your common ancestor (the 7th great-grandparents), and then nine generations down to your eighth cousin. This will bring you to a total of 18 degrees of separation – a truly distant relative.

What is a half-eighth cousin?

A half-eighth cousin shares only one of the 7th great-grandparents, instead of two. For example, if your 7th great-grandparent remarried after they were widowed, and your 8th cousin is descended from a child born from the second marriage, then you are half-eighth cousins.

How many eighth cousins do you have?

The average person might have as many as about 590,000 eighth (8th) cousins. That’s enough eighth cousins to populate the entire city of Milwaukee, Wisconsin.

Imagine an entire major city filled with your eighth cousins!

These nearly 600k 8th cousins will be descended from different sets of your 7th great-grandparents. We have about 512 ancestors nine generations back, which is how far we need to go to get to our great-great-great-great-great-great-great grandparents, and our 8th cousins will be descended from most of these ancestors.

Are there famous eighth cousins?

Due to the large number of eighth cousins that any given person has, there is a high chance that some of those cousins are famous. This means that there are many famous people that also have famous eighth cousins.

There are many examples, but I have chosen one to show in this article.

I was recently going through an old box of newspaper clippings that my great-great grandmother had made. Most of the clippings were in some way related to her genealogy research.

In one of her notebooks, I found that she had made clippings of a few articles that explained how the UK’s Churchill and the American President FDR were eighth-cousins once-removed. The information was printed in a few different newspapers and published around the time that they were having a series of meetings:

two old newspaper clippings on yellowed-paper with the titles "Franklin and Winston are 8th cousins!" and "What's Buzzin' Cousin? FDR could ask Winston"
Two newspaper clippings from the 1940s describing how Franklin D. Roosevelt and Winston Churchill were cousins

This information was of interest to my great-great grandmother because she was also descended from the ancestor shared between the two men. During the 1940s, genealogy research often depended on dubiously documented publications, and so the idea that these two famous people were related through Richard Warren has now been disputed.

However, there is a common ancestor shared between the two that makes them eighth cousins twice-removed. This different ancestor’s name was Arthur Howland, a brother of one of the Mayflower passengers.

Are eighth (8th) cousins blood related?

We are unlikely to share DNA with our 8th cousins. Eighth cousins have only about a .24% chance of showing up as DNA matches to each other.

People are often surprised to learn that we don’t share DNA with all of our relatives, but it’s true.

This means that if you and an 8th cousin take a DNA test, your eighth cousin will probably not be on your DNA match list. If every single 8th cousin took a DNA test, as unlikely as that would be, we would find about 1200 of them would show up as genetic matches to us.

Even though we aren’t likely to match one particular eighth cousin, since we have so many 8th cousins, we will find a large number of them through DNA testing.

How to find your eighth cousins

There are two main ways to find eighth cousins, should you be interested in finding them. They are through DNA testing and genealogy research.

As I mentioned above, a good number of those 590,000 eighth cousins would show up as a DNA match to you, should they decide to test their DNA. By testing your DNA with a company with a large database of testers, you will have the best chance of finding those 8th cousins.

At the moment, Ancestry has the largest database of DNA customers. Most people on the site have found that the have at least several thousand DNA matches, many of them matching very distantly (such as 8th cousins!).

If you aren’t interested in DNA testing, you can find 8th cousins through genealogy research by finding other people who are researching your distant ancestors. For example, take a look at public family trees on Ancestry that include information about your 7th great-grandparents.

There is a good possibility that some of the other people researching your 7th great-grandparents are also related to them the same number of generations that you are. These people would be your 8th cousins.


I hope that you have learned a lot about eighth cousins in this post, and that you now understand how you and your eighth cousins are connected. We have such a large number of cousins at this distance, which means that there is a seemingly endless number of people who can help us discover new details about our ancestry.

If you have any questions about something that you have read in this article, or you if you have a question about eighth cousins that you didn’t find the answer to, I would love to hear from you in the discussion below.

Thanks for stopping by!

Share the knowledge!

This site uses Akismet to reduce spam. Learn how your comment data is processed.


Monday 22nd of August 2022

I happen to be a descendant of Richard Warren so I was surprised to find his name in this article. He is my 12th great-grandfather.

This site uses Akismet to reduce spam. Learn how your comment data is processed.