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.
Another way is to take the person with the shortest distance to the common ancestor. Then think about how other descendants of that common ancestor would be related to them. Then subtract your generational distance from your match. For example, compare yourself with your father’s first cousin (the match). The common ancestor is your great-grandparents. Your match is older than you so he has the shortest distance in generations to your great grandparents. The common ancestors are the grandparents of your match. Other descendants of his grandparents would be his first cousins. But you are a generation away from the match. Therefore your relationship is a first cousin, once removed.
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 is a second cousin? A second cousin is someone who shares with you the same set of great grandparents. So think of two of your great 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 great great-grandparents, Giuseppe and Laura. Select that relationship in the first dropdown box. Then think about how Eleonora is related to my great 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:
Other Relationship Terms
Let’s talk about some other common relationship terms.
What is a third cousin?
A third cousin is someone with who you share a common set of great great grandparents. Remember the example above about my grandmother’s first cousin. Our common ancestors are my great 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 great great-grandparents, and we are the same number of generations away.
What is the cousin of my dad to me?
The cousin of your dad is also your cousin, but once removed. Whether it’s a first, 2nd, or third cousin, the idea is the same. You would have the same relationship to that cousin, just “once removed”.
What do I call my cousin’s child
Your cousin’s child would also be your cousin, once removed.
Are second cousins blood related
Yes. Second cousins are blood-related and are expected to share about 3.125% of DNA.
Most people never give this whole “once removed” idea much thought. They refer to their cousins as either close or distant and don’t really think about relationship terms. It’s when you start getting into genealogy, taking a DNA test, and building out the family tree 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!