Understanding the Family Tree – What is a 1st Cousin Once Removed?

A cousin once removed (or 1C1R) is one with whom you share one common ancestor but are separated by a generation. For example, your mother’s first cousin is a 1C1R. If that cousin has children, you are their nieces and nephews.

It gets a little more complicated if there are multiple generations between you and your cousin’s most recent common ancestor.

Your Parents’ Cousins

There’s no question that relationships between cousins can get pretty complicated, especially when several generations are involved. Keeping track of cousin-ness degrees isn’t always easy, but understanding how a person’s relative title applies can help you accurately fill out your family tree and correctly determine if someone is your first or second cousin, etc.

Your first cousin once removed, is the child of your cousin or the parent of your second cousin, indicating a generational difference in our family relationships.

When referring to your parent’s cousins, “once removed” indicates that they are one generation above or below you. For example, your dad’s first cousin is your first cousin, but if that cousin has children, those children are your first cousins once removed, as there is now a generation gap between you.

You’ll notice that the number of times a relation is removed increases with each generation. Thus, first cousins share grandparents. You are considered direct cousins if you and your first cousin have the same parents. However, if your cousin has grandchildren, you become first cousins once removed, and if that cousin has children, they are your second cousins once removed, as there is now ONE generation between you. The simplest way to understand this is to start with your most recent common ancestor and then work backward. This is how you’ll discover if someone is your first, second, or third cousin.

Your Grandparents’ Cousins

In some cases, cousins share a common ancestor but call the ancestor something different. This can confuse you when you are reading the family tree and wondering what relation to your cousin is. The first thing to remember is that cousins share blood and don’t need to have the same last name or live in the same place.

Next, remember that when someone refers to a cousin as once removed or twice removed, it means there is one generation of separation between you and your cousin. You can figure out this generation difference by counting how many “greats” are in the ancestor you share. This way, you can know what kind of cousin you are.

If the ancestor you share is your grandparents’, then you are first cousins. You are second cousins if the ancestor is your parents’ or aunts’ great-grandparents. If your ancestor is your grandparents’ siblings, you are third cousins.

If your cousin’s child has a child, you are that child’s first cousin once removed. If that child has another child, you are that child’s first cousin once removed twice. You can continue this pattern, moving up to fourth or fifth cousins as you move down the generations on your family tree. Remember, however, that these cousins are not your cousins if their parents are your parents’ or aunts’ siblings.

Your Grandparents’ Children

The relationships in your family tree are more complicated when you start talking about grandchildren, great-grandchildren, etc. These are called indirect relatives because you’re not sharing a direct parent-child relationship. Indirect relatives share grandparents, or more often, their parents and grandparents. But this is still a cousin relationship, just a different one than you might have as a first or second cousin.

Generations are counted from the most recent common ancestor between you and a particular cousin. The older you are removed from that cousin, the more distant your relationship will be. To help you understand this concept, looking at a cousin chart like the one provided by PLOS Genetics might be helpful.

This shows that your cousins are ranked according to their relationship with you by their number of shared grandparents. Those with the most shared grandparents are your first cousins. Second cousins share great-grandparents, and so on.

If your first cousin has a child, you and their child are first cousins once removed. If that child has a child, you and their child become first cousins twice removed. If that cousin has a child, you and their grandchild are first cousins three times removed. This numbering system can be confusing, especially for children of first cousins. But it’s helpful to know since your cousins’ children will account for many DNA matches in your genealogical software.

Your Grandparents’ Grandchildren

Navigating familial relationships can be confusing, especially when terms like “once removed” come into play. To be “once removed” from a cousin means that one generational ion is different from the cousin’s child. So, if you are talking about your first cousin’s child, they would be your first cousin once removed (or 1C1R).

The number of generations that separate you from a cousin determines how close or distant you are from them genetically and socially. Cousins who share the same great-grandparents are more immediate than those who have more than one generation in common.

For example, if you are their aunt or uncle, a first cousin once removed’s child is your niece or nephew. It is also expected to refer to grandchildren of relatives as nieces or nephews, even though the relationship is technically more closely defined as a first cousin once removed.

Once you understand the difference between cousins, it can be easier to keep track of how many times you are removed from a relative. But for those who struggle to grasp this concept, the critical point is that your cousin once removed’s ancestor is one generation closer to you than your parents. For this reason, they are your cousin. The more generations removed, the less DNA you will share with a cousin.