What Are Double First Cousins? (Explained)

The double first cousin relationship isn’t easy to understand with a dry statement.

It’s much clearer with an example and a picture. This article gives you both.

We’ll also dive into some questions around DNA and marriage. But let’s start with the basics.

What Is A Double First Cousin?

Both parents of a double first cousin are siblings to the parents of the other double first cousin.

The double first cousins share the same four grandparents.

Specific example

Here is one example of the relationship.

Two brothers meet two sisters and start double-dating.

One of the brothers marries one of the sisters. The other brother follows suit and marries the second sister.

The children of one couple are double first cousins to the children of the other couple.

In this example, we said that the fathers are brothers and the mothers are sisters.

It doesn’t have to be this way. The four parents must simply consist of two pairs of siblings (e.g. one brother/sister marrying another brother/sister).

Why “double”?

The reason why we use the term “double” is that the cousin relationship is through both the father and the mother.

They would be first cousins if only one parent was a sibling to the other. They are double-first because they are cousins twice over.

You and your double first cousins are of the same generation. You share all your grandparents.

What’s The Difference Between First Cousins And Double First Cousins?

Double first cousins are a closer relationship than first cousins.

They are interrelated through two family lines.

First cousins share two grandparents out of four. Double first cousins share all four grandparents.

Check out our separate article on first cousins. You can compare the diagrams here and there.

Do Double First Cousins Share DNA?

Double first cousins share about 25% of their DNA. This is similar to the amount shared by half siblings or between uncles and nephews.

It equates to about 1,500 centimorgans of shared DNA within a range of several hundred cM.

The reason for the variability is that people inherit different amounts of DNA from common ancestors. One cousin will receive DNA from a grandparent that the other doesn’t get.

Using DNA websites

If you’ve used one of the big commercial DNA testing services, you may be researching a list of DNA relatives who also tested with the same company.

The websites like Ancestry and 23andMe will give you a prediction of relationships based on the amount of shared DNA.

They currently cannot distinguish between double first cousins, half siblings, or uncles and aunts.

Be aware that the higher end of the range for first cousins may also overlap with the lower end of double first cousins.

Keep an eye out for labels of first cousin where the shared DNA is unusually high.

Can double first cousins not share DNA?

DNA from our ancestors gets reduced as it passes through generations.

Is it possible that it could all disappear within two generations? The answer is no.

Double first cousins will always share some DNA.

This will be enough to meet the thresholds of the major DNA testing sites.

In other words, if you and your double first cousin have both tested on Ancestry.com, you should be able to see each other listed as DNA relatives. 

Do Double First Cousins Count As Close Family?

This depends on whether the context is legal, genetic, or in day-to-day conversation.

In general, if a first cousin is considered close family, then the same applies to a double first cousin.

But in some legal contexts, double first cousins are marked out as being a closer family relationship.

For example, North Carolina allows first cousins to marry but prohibits double first cousins as it is a closer relationship. This is unusual in the United States.

Legal context

In many jurisdictions, including the United States, double first cousins are often considered close family in legal matters.

For example, if your employment has restrictions that mention close family then this probably includes double first cousins. An example is getting released from work to attend a funeral.

However, you should always check with the specific department (or state authority). Interpretations may vary across organizations.

DNA websites

If you’ve tested with a commercial DNA site, you may be researching your DNA relatives.

Some of the websites put a label of “close family” on some people in your list of relatives.

For example, Ancestry.com includes double first cousins in their close family category. You can read more in this section on Ancestry’s relationship labels.

Normal conversation

You see “close family only” on a funeral notice. Should you attend?

This depends on the culture and community. A double first cousin may be a stretch!

We suggest that you check discreetly with older members of the family.

Can You Marry Your Double First Cousin?

Nearly half of states in the United States do not allow marriages between first cousins or closer. A double first cousin will fall within this restriction.

Check out this section on first cousin marriage to get the detailed list.

North Carolina is an outlier in that the state allows marriages between first cousins but not between double first cousins.

Outside the U.S.

It may surprise you to learn that the United States is somewhat unusual in having these restrictions.

Many other countries have no restrictions on marriage between double first cousins. It’s legal in most European countries.

Can Double First Cousins Get Married In A Catholic Church?

Even though it may be perfectly legal to marry your double first cousin, there are other hurdles if you want to a Roman Catholic wedding.

Double first cousins must get permission from the local Archbishop in order to get married in a Catholic church.

The reason is due to Canon law.

Canon law and double first cousins

Canon law is quite specific on the cousin relationship, but it doesn’t actually mention the term “first cousin”.

Instead, the laws are based on counting the number of generations away from the common ancestors for the two potential spouses.

Each member of the double couple is two generations from their common ancestors, the grandparents.

These numbers are added together to come up with four degrees.

The Catholic Church refers to “consanguinity” when dealing with blood relations. So, the relationship is more specifically categorized as four degrees of consanguinity.

This is the same as plain old regular first cousins. The degrees aren’t halved because it’s genetically closer.

Regardless, Canon Law has special restrictions on church marriages within four degrees. This prohibition is on the local priest who can’t marry you without special permission.


A dispensation is special permission from the church hierarchy.

In earlier times, you would have to get the dispensation from the Vatican itself! However, the laws have been relaxed.

Double first cousins now need to get a dispensation from their local Bishop.

This may seem a little daunting. However, your local priest should help you with the application process.

Frequently Asked Questions

Here are some quick answers to common questions.

Are Double First Cousins Blood Related?

Double first cousins are blood relatives through two different lines. They share the same grandparents.

Are double first cousins siblings?

Double first cousins are not siblings. Double first cousins share grandparents, while siblings share parents.

Are double first cousins closer than siblings?

Double first cousins are more distantly related than siblings. Their common ancestor is one further generation away.

What is my dad’s double first cousin to me?

Your parent’s double first cousin is your double first cousin once removed.

What are double second cousins?

The children of double first cousins are double second cousins to each other.

Margaret created a family tree on a genealogy website in 2012. She purchased her first DNA kit in 2017. She created this website to share insights and how-to guides on DNA, genealogy, and family research.

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