What is a Fourth Cousin?

Marc McDermott
First Published: | Updated: April 2, 2024

What is a fourth cousin and how are we related to one another? It can be difficult to track your family tree the bigger it seems to get, so we’re going to cover all the burning questions about fourth cousins. 

The more generations involved, the more complicated it becomes to research a family tree. To shed some light on the ins and outs of fourth cousins, we’ll cover topics such as whether or not they share DNA, what being a half-fourth cousin means, “removed” fourth cousins, and a lot more. 

So, what is a fourth cousin?

A fourth cousin is someone who shares a set of great-great-great-grandparents with you. Essentially, they are the descendants of a sibling of your great-great-grandparents. Any number of cousins is an example of how many generations you are away from your common ancestor. 

fourth cousin

So second cousins share a great-grandparent, and third cousins share a great-great-grandparent. Subsequently, fourth cousins share a great-great-great grandparent, marking what is the 5th generation in your family tree.

How is a fourth cousin related to me?

A fourth cousin is related via great-great-great-grandparents. Fourth cousins are both descendants from the same number of generations away from a common ancestor – when considering fourth cousins, this is five generations. 

A fourth cousin that is once removed is a child of your fourth cousin. Two cousins that share the common ancestor but do not share the same number of descending generations are considered “removed”  

Those closest to the common ancestor set the cousin relationship, whether this is first, second, third, fourth, etc. “Removed” is used to calculate from this person’s generational level. 

Are fourth cousins considered family?

Although fourth cousins do not seem to be close in relation, they are considered family. Some may say they are not close family, but with DNA shared with some cousins, it is prudent to say fourth cousins are family. 

Are fourth cousins blood-related?

Because you only share DNA with around half of your fourth cousins, there is a chance that you are not “blood-related.” 

If you have a half-fourth cousin, it is more likely that you do not share identical DNA. You may be genetically related to each of your fourth cousins, but it is possible to not share DNA with all of them. 

What grandparents do fourth cousins share?

Fourth cousins share a great-great-great-grandparent. This, in turn, means second cousins share a great grandparent and third cousins share a great-great-grandparent. 

It is possible to share a complete set of great-grandparents with a fourth cousin, although anyone who shares one great-great-great grandparent would technically be a half-fourth cousin. 

With 32 great-great-great-grandparents, you will share 2 of the 32 with a fourth cousin. For a half-fourth cousin, you will only share 1 out of the possible 32 great-great-great-grandparents. 

How many fourth cousins do I have?

The number of relatives anyone has in a generation can depend on a handful of variables. 

To start, if all your great-great-great-grandparents had lots of kids and their kids survived to become adults and had lots of kids themselves, then you are more likely to have more fourth cousins than the average family tree. 

However, other factors including not having multiple kids, war, illness, natural disasters, and other factors can reduce the number of fourth cousins you have. This can mean you have fewer fourth cousins than the average person, so it is difficult to put an exact number on how many fourth cousins anyone has. 

What does fourth cousin once removed mean?

The child of your fourth cousin or the fourth cousin of your parent is known as a fourth cousin once removed. Two cousins that share a common ancestor but are not the same number of generations from great-grandparents are said to be “removed.”

Cousins that are not removed share the same generation. To put this into context, a first cousin is the child of your parent’s brother or sister. As your parents and their siblings were part of the same generation, so are you and their siblings’ children. 

No matter which cousin it is, a cousin that is once removed is one generation above or below another.

This means your mom’s first cousin is your first cousin, but he or she is once removed because of the generation between the two of you. 

If your fourth cousin was to have a child then their child would be once removed because they are one generation below you. 

What does fourth cousin twice removed mean?

For there to be “removed” in a relationship, the cousins must not share the same generation. A fourth cousin that is twice removed is a fourth cousin who is two generations away from yours, either older or younger. 

If a cousin is not removed, it means they are part of your grandparents twice removed, it means your cousin will either be a part of your grandparent’s generation or the same generation as your grandchildren as there are two generations between you.

What is a half-fourth cousin?

Anyone descended from a half-sibling of your great-great-grandparents is considered your half-fourth cousin.

Essentially, you only have one mutual great-great-great grandparent in common. It is important to distinguish between the two when researching a family tree if you are following your bloodlines and heritage.

Final word

To sum it up, two people that share one great-great-great-grandparent but not the other are half-fourth cousins. 

Read more about kinship.

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