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How to Calculate Cousin Relationships

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The article describes how to define the relationship of cousins and the terms used by genealogists when doing family research.

Genealogists are conscious of the relationships between family members. The way the relationships are described is somewhat complicated and gives rise to confusion. Understanding the meaning of the various designations of family relationship will help clear up the confusion.

Most people understand the close relationships like parents, brothers and sisters, aunts and uncles, and grandparents. The most confusing of the family relationships come when cousins become involved. In this article I will try to describe the relationships in two ways: One way will use as a starting point an ancestor that two people share. The other involves the connection between the two people.

We all have two sets of grandparents, but it only takes one of them to provide the cousin relationship. You and your first cousin will share a set of grandparents. That’s pretty simple. One of your parents and one of your cousin’s parents are brothers or sisters. If you and your first cousin both have children, they will be second cousins. If the second cousins have children, they will be third cousins. And all these people will have the same set of ancestors: for the second cousins, the common ancestors will be great grandparents, and for the third cousins, the ancestor will be great-great-grandparents.

That’s not too bad as long as everybody keeps the generations even. The complication comes when we try to keep straight relationships that cross generational lines. If your grandfather is also the great-grandfather of another person, you are cousins, but what kind? The trick is to count how many generations it is back to the common ancestor for each of you and subtract to find the difference. In this example, you will subtract 3 from 4 and get 1, and that will make you first cousins once removed.

In my own family research I found that my husband’s family is related the Daniel Boone. My husband is 8 generations from George Boone III. Daniel Boone is the grandson of George Boone III, or he is three generations from George. Subtract 3 from 8 and we find that my husband relationship to Daniel Boone is first cousin five times removed. I’m not sure why that was such an exciting thing for me, but it is at least interesting.

When you are doing research, especially in older records, the differences in degree of relationship may be more complicated because of customs. Close cousins may be referred to as brothers, or all cousins may be lumped into one category. Some people who were cousins were referred to as aunt or uncle, and everybody was called “cus’n.” In letters and social documents these titles may have described emotional ties rather than family relationships.

The chart below will give you the basic pattern for sorting out the cousin thing. Extend it as far as necessary using the same logic. The top left-hand cell is the common ancestor. The first column is the relationship of one person to him or her, and the top row is the relationship of the other person to the common ancestor. Where the row and the column intersect defines the relationship of the two people you are dealing with.

Common ancestor child gramdchild g-grandchild g-g-grandchild g-g-g-grandchild
child siblings



grandchild neice/nephew 1st cousin 1st cousin once removed 1st cousin twice removed 1st cousin three times removed
g-grandchild great neice/nephew 1st cousin, once removed 2nd cousin 2nd cousin once removed 2nd cousin twice removed
g-g-grandchild g-g neice/nehped

1st cousin, twice removed

2nd cousin once removed 3rd cousin 3rd cousin, once removed
g-g-g-grandchild g-g-g neice/nephew 1st cousin three times removed 2nd cousin, twice removed 3rd cousin, once removed 4th cosin

Greet your cousins at the next family reunion and sort out your relationships.  It will be a lot of fun.  If you are nterested in pursuing family research the following sites may help you.

How to Use the Heritage Quest Online Website for Family Research

How to Search USGenWeb.org for Family History Details

How to Begin a Family History

How to Create an Oral History of Your Family


About This Article

Gayle Haynes

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