How to Calculate Family Relationships: Cousin Chart (part 1)

Many of us are lucky to have large numbers of people we can call family. In terms of relationships, these family members are divided into close or distant, based on how you are related to them.

For a lot of us, family relationships are complicated to understand, especially in the case of distant relatives. While having a first cousin is fairly straightforward, it can be hard to make sense of your line of relatives stretching into second, third, and fourth cousins.

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Then there’s the dilemma of terms like “first cousin once removed,” further adding to the confusion – and that’s where a cousin chart can be invaluable. Also known as a table of consanguinity, a cousin chart provides a visual representation of your relationship with your cousins. It can help you track down how you are connected to other individuals with common ancestors.

Understanding Cousin Relationships

The term cousin is highly generic as it is used to denote our relationship with most individuals who belong either to our maternal or paternal side. In short, it is a broad term that encompasses all individuals with whom we are related by blood ties beyond the direct parent-child relationship. Cousins can be separated in terms of degrees (the number of generations between each cousin and their nearest common ancestor).

What Is a First Cousin?

This one is the easiest cousin relationship to understand: it simply means you share the same grandparent(s).

What Is a Second Cousin?

Whether a relative in question is your second, third, or fourth cousin has to do with the number of generations that lie in the way of your common ancestor. Here’s a breakdown of this:

• First cousins share a grandparent who is 2 generations away
• Second cousins share a great-grandparent who is 3 generations away
• With third cousins, you share a great-great-grandparent who is 4 generations away
• Fourth cousins share a 3rd-great grandparent who is 5 generations away

A quick tip would be to count how many “greats” are in your common ancestor’s title to find out what number of cousin your relative is. With grandparents, no prefix of great is added which is why cousins who share the same grandparents are classified as first cousins. Keep in mind that this trick works only in cases when you and your cousin are the same number of generations distant from the common ancestor.

What Does It Mean When a Cousin Is “Once Removed”?

What ties together first, second, and third cousins, and so on is the fact that they share the same generation as one another. This means that their shared ancestor is located at the same position in the family tree for these cousins or the same number of generations have elapsed down to the current lot of cousins. However, if you and your cousin differ with respect to one generation or your cousin is a generation older or younger than you, the term removed better fits your genealogical situation.

If you share a common ancestor with a cousin who differs one generation from you, you would be said to be once removed. The number before removal specifies the number of generations you are separated from your cousin. Let’s consider that a common relative for you and your cousin is your grandfather – but for your cousin, he happens to be her great-grandfather. In other words, you count back two generations to your shared ancestor, whereas your cousin counts back three. Since there is a one-generation difference between you both, you would be classified as first cousins once removed. Carrying this logic forward, you would be labeled as twice removed if there is a difference of two generations above or below you, and so on.

What Is a Cousin Chart?

Ever wondered how exactly you’re related to someone in your family? A cousin chart can help clear up the confusion and give you a clearer picture of your relationship with that person. Think of it as a visual tool that helps map out family connections and shows the exact relationship between two relatives.

Cousin charts make it easier to understand where people fit in your family tree. They work by numbering cousins based on how many generations back you share a common ancestor, and how many generations apart you are. This helps explain both the degree of cousinship and how “removed” someone is from you.

How to Use a Cousin Chart

Here’s a series of steps to follow when using a cousin chart.

(1) The very first step is to pin down the grandparents or ancestors that you and your cousin share. For example, your fifth grandparent is your cousin’s seventh grandparent.

(2) Tracing your finger along a horizontal line, find the grandparent that’s common to you both. You will have to count the number of generations you are removed from this ancestor, which may vary for you and your given relative.

(3) Do the same for the vertical line to find your cousin’s shared grandparent.

(4) Locate the intersection of the vertical line cutting through the horizontal line. The point at which the two lines connect gives you the precise coordinates of your relationship. As per the previous example, it can be evaluated that you are 6th cousins two times removed.

Click here to download your free cousin chart. (This download will be a .pdf document that you can enlarge to make it easier to read and use.)

Coefficient of Relationship

You probably dealt with coefficients in the past during a math class. You may find it amusing to know that coefficients can be applied to relationships also. The coefficient of relationships quantifies the extent to which two individuals share a similar genetic makeup. It takes the form of a percentage to represent the proportion of shared genetic material between two related individuals. There are some pre-determined coefficients as far as certain close relations are concerned.

• Siblings share approximately 50% of DNA.
• Between first cousins, the shared DNA is approximately 12.5%.
• It is reduced to merely 3.125% among second cousins.

Understanding how coefficients work is central to fields like genetics and genealogy, where it provides a means to assess the degree of closeness of relationships. A higher coefficient of relationship means that you are closer together on your family tree.

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Use Math to Calculate Family Relationships

If you are a fan of math, you will enjoy playing around with numbers to calculate your cousinship. Before you dive deeply into mathematics, you need to answer the following three questions:

(1) Who is the common ancestor linking me and my cousin?

(2) How many generations are we both separated from this ancestor? This would be calculated separately. You simply have to count the number of G in the title of your common ancestor and add 1.

(3) Next, you need to figure out who among you two is more removed from a common ancestor. This is expressed in terms of the generational difference between you and the ancestor.

The next steps to follow drive from the number of generations both you and your cousin are from the common ancestor.

(1) Same number of generations away from your common ancestor

Suppose that the nearest ancestor common between you and your cousin is your great-great-grandparents.

Starting out, we will note how many “greats” are in your common ancestor’s title and add 1. The value you get is the correct way to label your cousin.

Since there are 2 greats in the title of your shared ancestor, this can be computed as 2 “greats” + 1 = 3, so you are third cousins to each other.

Since there is no generation gap between you and your cousin, you both are part of the same generation. In other words, you are both at the same level in a cousin chart and hence not removed from each other.

(2) Your cousin is closer to your common ancestor

Suppose that you and your cousin have a common ancestor who is your cousin’s great-grandparent, but you’d call him your great-great-grandparent. In other words, your cousin’s family tree will show less steps than yours in reaching from you to your shared ancestor.

The calculation would proceed as follows:

Count the number of greats in your shared ancestor’s title and add 1 to that. This will give you the correct number label for your cousin.

Following the above example, it would look like this: 1 “great” + 1 = 2, so this is your second cousin.

Next, you need to determine how removed this cousin is from you. For this, you need to deduct the number of generations between your cousin and the common ancestor with the number of generations you are separated from the common ancestor.

Since your great-great-grandparent is your cousin’s great-grandparent, then you are 4 generations away from him while your cousin is 3 generations away.

4 generations – 3 generations = 1 generation, meaning that this cousin of yours is a cousin once removed.

Adding this to the number calculated earlier, this collectively makes him your second cousin once removed.

(3) Your cousin is further away from your common ancestor

Consider a scenario where your cousin has a great-great-grandparent who is your great-grandparent. This suggests that you are nearer to the ancestral line than your cousin.

Again, count the number of greats in your shared ancestor’s title (a great-grandparent to you) and add 1 to that. This will give you the correct number label for your cousin.

Following the above example, it would look like this: 1 “great” + 1 = 2, so this is your second cousin.

Then, you will 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 tells you how removed this cousin is from you.

There is a difference of 4 generations between your cousin and his great-great-grandparent, whereas you are 3 generations removed from the common ancestor.

Adding this to the number calculated earlier, this collectively makes him your second cousin once removed.

In tomorrow’s part 2, we will explore such concepts as Parallel vs. Cross Cousins, and Double First Cousins. We will also discuss practical benefits of knowing your cousin connections.

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