What Is a Second Cousin?: How to Calculate Family Relationships

July 23, 2019  - by 
Happy cousins eating ice-cream

Trying to figure out what to call your distant cousin? Even if you know what it means to be a second, third, or fourth cousin (and if you don’t, check out this simple, visual article for an explanation), it can be hard to identify these relationships in real life. Even a question as simple as “What is a second cousin?” can be tricky. That’s where the cousin calculator comes in handy—but knowing the basics is also a good place to start.

Cousins: The Basics

Cousin Chart

How do Cousins Work?

Cousins share a common grandparent. The cousin label (first cousin, second cousin, etc.) changes depending on which grandparent the cousins share.

What is a Second Cousin?

A second cousin is a someone who shares a great-grandparent with you.

What is a Second Cousin Once Removed?

A second cousin once removed is either the child of your second cousin or the parent of your third cousin. They are “once removed” because you are separated by 1 or more generations.

For a more in-depth look at cousins and what it means to be “removed,” check out our Cousin Relationships Explained article. Or, if you have a more complicated cousin relationship to calculate, use the chart below.

The Cousin Calculator

Quickly figure out how you are related with this fast and easy to use Cousin Calculator!

First, select how you are related to the common ancestor. For example, if the common ancestor is your great-grandparent, select “great grandparent” from the first drop-down menu. Then select your cousin’s relationship to the common ancestor. The calculator will use this information to tell you how you are related!

Calculate your relationship to another cousin based on a common ancestor.

The following cousin calculator (click to enlarge) can also help you figure out what to call your more distant cousins.

Cousin calculator, relationship chart

To use the chart, follow these steps:

1. Identify the grandparents you and your cousin share.

  • Example: Your 5th great-grandparent is your cousin’s 7th great-grandparent.

2. On the horizontal line, find your shared grandparent.

  • Example: Your 5th great-grandparent.

3. On the vertical line, find your cousin’s shared grandparent.

  • Example: Your cousin’s 7th great-grandparent.

4. See where the lines intersect.

  • Example: You connect the lines and see that you are 6th cousins, 2x removed.

How to Calculate Cousinship Using Math

If you enjoy math, you can also calculate your cousinship using the following method, which starts by asking three questions:

1. Who is the common ancestor of my cousin and me?

2. How many generations am I separated from this ancestor? How many generations is my cousin separated from this ancestor?

  • Hint: Count the number of “G’s” in the common ancestor’s title and add 1. For example:
    • Your Grandparents (1G + 1 = 2) are 2 generations away
    • Your Great-Grandparents (2Gs + 1) are 3 generations away
    • Your Great-Great Grandparent (3Gs + 1 = 4) are 4 generations away

3. Who is more removed from the common ancestor?

  • Hint: The person more removed from the common ancestor is the person whose common ancestor is more generations away.

The next steps will be different depending on how many generations both you and your cousin are from your common ancestor.

If you are both the SAME number of generations away from your common ancestor:

Example: The common ancestor is both you and your cousin’s great-great grandparents.

1. Count how many “greats” are in your common ancestor’s title and add 1. This will give you the correct number to label your cousin as.

Example: You and your relative share great-great grandparents. There are 2 “greats” in this title. 2 “greats” + 1 = 3, so you are third cousins.

2. Because you are the same number of generations separated from each other’s common ancestor (meaning you are of the same generation), you and your cousin are not removed from each other.

If your cousin is FEWER generations away from your common ancestor than you are:

A grandmother with her grandchildren.

Example: The common ancestor is your cousin’s great-grandparent and your great-great grandparent

1. Count how many “greats” are in your cousin’s common ancestor’s title and add 1. You now have the correct number label for your cousin.

Example: The common ancestor is your cousin’s great-grandparent. 1 “great” + 1 = 2, so this is your second cousin.

2. Subtract the number of generations your cousin is separated from the common ancestor from the number of generations you are separated from the common ancestor. The answer is how removed this cousin is from you.

Example: If your great-great grandparent is your cousin’s great-grandparent, then you are 4 generations removed and your cousin is 3 generations removed from your common ancestor. 4 generations – 3 generations = 1 generation removed, so this is your cousin once removed.

In this scenario, your relative is your second cousin once removed.

 If your cousin is MORE generations away from the common ancestor than you are:

Example: The common ancestor is your cousin’s 3rd great-grandparent and your great-great grandparent

1. Count how many “greats” are in your common ancestor’s title and add 1. Now you have the correct label for your cousin.

Example: If the common ancestor is your great-grandparent, there is only one “great” in this title. 1 “great” + 1 = 2, so this is your second cousin.

2. Subtract the number of generations you are separated from the common ancestor from the number of generations your cousin is separated from the common ancestor. The answer is how removed this cousin is from you.

Example: If your cousin’s 3rd great-grandparent is your great-grandparent, then your cousin is 5 generations removed and you are 3 generations removed from the common ancestor. 5 generations – 3 generations = 2 generations removed, so you are my cousin twice removed.

In this scenario, your relative is your second cousin twice removed.

Discover Your Family

What with all your second, third, and fourth cousins and grandaunts and granduncles, your family tree is much larger than just your direct line. Discover more about your family by starting your own family tree at FamilySearch.

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Comments

  1. How is it that one of my 3rd cousins has 7cMs and the other 3rd cousin sharing the same gr x 2 grandparents has 57cMs?

  2. I read that the children of my mother’s first cousins were my second cousins. Is that not correct?

  3. To answer your question, we would have to ask you to not identify the person’s relationship to you but rather which generation of grandparents you share. Thenemploy a shift constant if necessary to balance the equation.

  4. What if we share a common grandfather but not a common grandmother. Are we still 1st cousins? Or are we 1/2 cousins?

  5. If the two of you share just one grandparent, you are half first cousins. It’s like two people sharing just one parent: the second person would be a half brother or half sister of the first, and vice versa. Historically, there has been controversy over whether a man should marry his deceased wife’s sister, but if he did, and had a child with each sister, they were three-quarter siblings, and the grandchildren might be three-quarter first cousins.

  6. how do you calculate your cousin if your father’s brother married your mother’s sister? what does than make my cousins children to me?