The term “once removed” in genealogy refers to the number of generations separating two cousins. A first cousin once removed can be a first cousin of your parent or a child of your first cousin. Start with the two people of the same generation who share a common ancestral couple, then subtract your generational difference.
The easiest way to think about this is to picture a first cousin of one of your parents. Let’s call him Sam. Sam and your parent are full first cousins. They are in the same generation and share a set of grandparents. Because you are one generation away from your parent, you would be first cousins once removed with Sam. Make sense?
It also works in the opposite direction. Now think about one of YOUR first cousins. We’ll call her Marie. Marie has a daughter named Rose. You and Marie are full first cousins because you share the same grandparents and are the same generation. So then, what is your relationship with Rose? You’d be first cousins once removed because there’s one generation between Rose and Marie.
Now let’s imagine Rose had a child named Lilly. Lilly is the granddaughter of your first cousin, Marie making her two generations away. Therefore your relationship with Lilly is first cousin, twice removed.
Second Cousin vs. a First Cousin Once Removed
Let’s talk about second cousins. Some people confuse first cousins once removed with second cousins. What are second cousins? A second cousin is someone who shares with you the same set of great grandparents. So think of two of your grandparents, then think about your cousins who descend from them of the same generation as you. Or think about your grandparent’s siblings. Got one in mind? Their grandchildren would be your second cousins.
I created this cousin calculator to help you visualize your cousin relationships:
Relationship to Common Ancestor
The first step in using this calculator is to identify the common ancestor between yourself and your cousin. Let’s use the example of my grandmother’s first cousin, Eleonora. Who would be the common ancestors? It would be my 2x great-grandparents, Giuseppe and Laura. Select that relationship in the first dropdown box. Then think about how Eleonora is related to my 2x great grandparents? They are her grandparents. Select that relationship in the second dropdown. You can optionally input the names of all parties if you want a more personalized visualization. Then click ‘Calculate.’ In our example, the graph will look like this:
What is a third cousin?
A third cousin is someone with who you share a common set of 2x great grandparents. Remember the example above about my grandmother’s first cousin. Our common ancestors are my 2x great grandparents. But now, let’s imagine that my grandmother’s first cousin had grandchildren of her own. They would be my third cousins because we share the same set of 2x great-grandparents, and we are the same number of generations away.
Most people never really give this whole once removed idea much thought. They refer to their cousins as either close or distant. It’s when you start getting into genealogy, taking a DNA test, and building out your family that you begin to think carefully about these fascinating cousin relationships.
Now, pick out one of your more distant cousins and see if you can figure out the relationship!