What is a Fourth Cousin?

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

Tests from sites such as Ancestry and 23andMe are undeniably very beneficial in helping break through some family history brick walls. You can find literally hundreds of people who share common DNA with you who, to varying degrees, might be related to you.

If your close family have taken tests as well they will show up as very obvious matches. That is of course assuming that there is no hidden family secret that is going to get blown wide open. Generally speaking, however, the mysteries start with the third cousin matches and beyond.

These more distant cousin matches are very often people you do not know on a personal level and they can be a great source of information for the research in your more distant family tree. For example, a fourth cousin seems so distant but how exactly are you related?

What Are Fourth Cousins?

You might imagine that a fourth cousin may be a complicated relationship to understand but actually, this is not the case. If you have a fourth cousin match this likely means that you share a set of great-great-great-grandparents.

These great-great-great-grandparents are the parents of one of your great-great-grandparents and also the parents of your fourth cousin's great-great-grandparent. The children from these great-great-grandparent siblings were first cousins to each other. The children of those first cousins are second cousins. This carries on down the line with those second cousins' children being third cousins before finally, the children of the third cousins are you and your fourth cousin.

Phew! Are you confused enough yet?

To make this more clear each successive generation of children from siblings have a cousin match and a corresponding number. First cousins then are the first generation, second cousins are the second generation and so on.

How Closely Are We Related to Fourth Cousins?

In terms of everyday family life, it is somewhat unlikely that you might have regular contact with a fourth cousin. There are four generations between you and the common ancestors you share with your fourth cousin.

It is extremely rare for anyone to have ever met their great-great-great-grandparents although not impossible. This does not mean that people never meet fourth cousins because huge family reunions at one point were very popular in the United States.

Most people today, however, find their fourth cousins through a shared interest in family history. This may be through common ancestors found in the trees of others on Ancestry or a DNA match. It is important to note though that we only share DNA with about half of our fourth cousins.

The nature of DNA recombination in inheritance means that it is very common that we do not share blood with our fourth cousins. In an ideal world of DNA inheritance, we would receive about 3.12% of our DNA from each of our great-great-great-grandparents. In truth, it is entirely possible that we receive no DNA at all from some of these ancestors.

How Many Fourth Cousins Do You Have?

It is easy to know how many grandparents or great grandparents a person has as this is generally a simple thing. You can also make a decent estimate of the average number of siblings, first cousins or second cousins someone might have. This is not the case with fourth cousins.

There are so many variables involved including differing family sizes, historic large scale death events and religious affiliations. Potentially you could have hundreds even thousands of fourth cousins but tracing them all would be time-consuming.

Other Fourth Cousin Terms

There are also several other terms in which the fourth cousin is used that relate to slightly different relationships. These include:

• Fourth Cousin once Removed: This is the relationship between you and the child of your fourth cousin
• Fourth Cousin twice Removed: This is the grandchild of your fourth cousin
• Half Fourth Cousin: This means that your respective great-great-grandparents were only half-siblings, making you only half fourth cousins

Neil Edwards

Genealogist and family-tree research specialist

Neil was born in Shropshire, England surrounded by centuries of living history. His interest in the past has been a lifelong passion leading to undergraduate degrees in both Economic History & Geography and History & Politics.

This interest in history quickly translated to family history when he moved to the U.S. in 2010. It was here that he began working on his own family tree as well as that of his American wife. That research allowed him to gain a wealth of experience working with both U.S. and European genealogical documents and studying their best uses in researching family history.

Following 9 years of honing his genealogical research skills, Neil was proud to have earned a certificate in Genealogical Research from Boston University in late 2019. Neil also took part in the research process for a Duke University study into the families of 19th Century UK Members of Parliament.

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