Can Fourth Cousins Marry Each Other? (2024) | Genetics Ancestry

Fourth Cousin

As a family gets bigger, it becomes more difficult to keep track of who is who.  When there are a huge number of generations involved, it becomes very difficult to research a family tree. Family trees can be as intricate as the branches of a sprawling oak, filled with distant relatives and connections that may seem perplexing at times. Within this intricate web of kinship, terms like “fourth cousin” might raise questions. Just how genetically related are fourth cousins? Are they considered blood relatives? Can you even be fourth cousins with someone?

Let us take a closer look at who fourth cousins are and their genetic connections, Before delving into the specifics of fourth cousins, let’s establish some groundwork by exploring cousin relationships in general. First, there is what we commonly refer to as “first cousins.” These cousins share a set of grandparents. When two people are siblings and each has a child, those children become first cousins.

Then, we have “second cousins.” Second cousins share a set of great-grandparents. To break it down further, when two individuals are first cousins, and each has a child, those children become second cousins.


What is a Fourth Cousin?

Now, let’s zero in on fourth cousins. To understand this, we need to grasp the concept of generational separation. Fourth cousins share a set of great-great-great-grandparents. This means that if you and another person can trace your ancestry back to the same set of people who lived several generations ago, you are considered fourth cousins.

It’s important to note that cousin relationships become more distant as the number of generations between them increases. This means that fourth cousins are more distantly related than first, second, or third cousins.



How Much DNA Do Fourth Cousins Share?

It has been established that you only share DNA with about half of your fourth cousins so there is a huge possibility that you are not ‘blood related’. In the case of a half-fourth cousin, it is even more likely that you do not share identical DNA. You can be related to each of your fourth cousins genetically, but there is a likelihood that you do not share DNA with all of them.

How Genetically related Are Fourth Cousins

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

Fourth Cousins vs. Fifth Cousins

This paragraph answers the question: are 4th or 5th cousins blood related? Have you ever wondered whether fourth and fifth cousins are blood related? Yes, both fourth and fifth cousins are related. They share a common blood line, although separated by generations. Fifth cousins have the same great-great-great-great-grandparents, one generation behind fourth cousins who share great-great-great-grandparents.

For clarity, if you ever wondered if 4th or 5th cousin’s blood related, although they are relatively distant relatives, both fourth and fifth cousins are part of your extended family. This is also because fourth cousin DNA is shared.

Can You Be Fourth Cousins with Someone?

I suppose the first question one should ask is what is a fourth cousin? It is possible to be a fourth cousin with someone, but it might need some serious research to find the connection. To know if you are fourth cousins with someone, you need to look back at your family tree and go back a number of generations and find a common pair of great-great-great-grandparents.

It is important to remember that as you go back in generations, the amount of potential fourth cousins will increase significantly. This is because the number of relatives from one pair of great-great-great-grandparents can be very huge. So, even though you may have many fourth cousins, you might not know about them until you have done a very detailed study of your family history.

About Fourth Cousins and Marriage

A very common question that usually comes up is whether fourth cousins can marry each other. Because we have established what is a fourth cousin, we can now look at it from a genetic point of view. You must remember that fourth cousins are actually already distant relatives, which means that their genetic similarity is minimal. Therefore, there is generally very little risk of any birth defects in relation to fourth cousin marriages.

Actually, it is very possible for people to marry their fourth cousins without even realizing that there is a family connection. This being said, the appropriateness of cousin marriages is different in every culture and religion, in different parts of the world.

Fourth Cousins Once Removed

What does it mean to be a fourth cousin once removed? When we say “once removed” in reference to a cousin relationship, it means that there is a generational gap. For example, if your father is fourth cousins with someone, it therefore follows that, that person would be your fourth cousin once removed. In the same breath, if you are fourth cousins with a person and that person is a generation older or younger than you, they are your fourth cousin once removed as well.

This idea might seem a little bit confusing, but it is only a way to explain the generational difference inside a cousin relationship. Fourth cousins once removed are still considered distant relatives, and they do have the same pair of great-great-great-grandparents, the only difference is that they belong to different generations within the same family.

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To further explain, 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 Matt, a cousin that is one generation above or below another. This means that your mother’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. That is what the fourth cousin twice removed means.

Fourth Cousins vs. Third Cousins

In order to get a clearer picture, let us briefly discuss third cousins. Third cousins have the same great-great-grandparents, which is one generation closer to you than fourth cousins who have the same great-great-great-grandparents.

With regard to the genetic relationship, third cousins share only about 0.78% of their DNA with you, which is more than the 0.20% you share with your fourth cousins. This means, therefore, that third cousins are more closely related to you, although they are still considered distant relatives in the larger picture of family relationships.

How Many Fourth Cousins Do I Have?

The number of relatives that a person has in a generation can depend on a number of variables. T start, if all your great-great-great-grandparents had lots of kids and their kids survived to become adults and had a lot of kids themselves, then you are most 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 will have. This can mean that you will have much fewer fourth cousins than the average person, so it is difficult to put an exact number on how many fourth cousins anyone has.

Fourth Cousin Chart

To help get a clearer picture about the connections between our cousins, we can refer to a cousin chart. This chart shows us the relationships between different cousin levels by looking at the number of generations that are between them. Here’s a simple fourth cousin chart, for example:

  • First cousins share a grandparent (2 generations)
  • Second cousins share a great-grandparent (3 generations)
  • Third cousins share a great-great-grandparent(4 generations)
  • Fourth cousins share a 3rd-great grandparent (5 generations)

cousin chart
cousin chart

This chart can continue for more distant cousins, with every level indicating an additional generation removed from the common ancestors.

Can You Date Your Fourth Cousin?

It is possible to date your fourth cousin because even though you are related, the relationship connection is very distant. It is true that you share DNA, but the amount of it is so small that it becomes insignificant. To be exact, the amount of DNA that you share with a fourth cousin is zero point four. This means that you can date and even get married without there being a risk of genetic deformity. 

Even though some societies might not agree with dating fourth cousins, there are those that do not have a problem with it. In the end it should be a personal choice.

How Third Cousins and Fourth Cousins Are Related

Now that we have covered the basics of third and fourth cousins, let us see how these relationships fit into your extended family.

  • Your third cousin shares a set of great-great-grandparents with you.
  • Your fourth cousin shares a set of great-great-great-grandparents with you.

If you can imagine your family tree with many branches, then your third and fourth cousins are distinct, but distant, branches. These branches move further from your direct family line, but they are still a part of the larger family tree.

What Is a Half-Fourth Cousin?

Anyone that is descended from a half-sibling of your great-great-grand-parents is called your half-fourth cousin. Essentially, you only have one mutual great-great-great grandparent in common. It is important to differentiate between the two when researching a family tree if you are following your bloodlines and heritage.

Even though the concept of half-siblings is widely understood by most people, you may be wondering if there is such a thing as a half-fourth cousin. Well, half-cousins do exist, although they are very rare.

A half-fourth cousin happens when one of your parents, like your father, is a half-sibling to one of your fourth cousin’s parents. Whoa, that is a mouthful, isn’t it? What this means is that, there is a half-sibling relationship somewhere along the line in your family that goes back to your shared great-great-great-grandparents. Because of this, there is a genetic connection that is more complicated than that of the usual fourth cousins, as it involves both full and half-sibling relationships within the family tree.

Final Words

Understanding the dynamic relationships between cousins, fourth cousins included, can shed light on your extended family connections and the genetic ties that bind you together. Fourth cousins share a set of great-great-great-grandparents and are considered blood relatives, although distant ones. 

The idea of fourth cousins once removed introduces an extra layer of complexity to these relationships, indicating generational differences within the cousin connection. While the genetic relationship between fourth cousins is minimal, factors like cultural norms and personal preferences may influence whether people choose to date or marry their fourth cousins.

So, the next time you hear the term “fourth cousin,” you can confidently navigate the branches of your family tree.


How are fourth cousins related to each other?

Fourth cousins share a set of great-great-great-grandparents.

What is the probability of sharing a common ancestor with a fourth cousin?

The probability of sharing a common ancestor with a fourth cousin is approximately 16%.

Are there any genetic similarities between fourth cousins?

Fourth cousins share a very small amount of DNA, typically around 0.1%.


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