Understanding kinship terms like “once-removed” and “twice-removed” is an important part of family history. These suffixes help to describe the gap in generations between cousins and are also used in DNA matches.
To determine your relationship to a relative, count the number of greats in their title and add 1 to determine how many generations separate you.
Look at Your Parents
What is a 1st cousin once removed? A family member shares an ancestor with you two or more generations ago. Your first cousins share grandparents with you; your second cousins share great-grandparents, and so on. The “removed” part comes into play because we count the generation differences between you and your relative to determine your relationship.
You and your sister have the same father and mother but live a generation apart. That makes you both first cousins. But your sister’s son lives another generation away. That child is your first cousin once removed because you and her share a parent but are separated by one generation.
The “removed” part also applies when talking about other relatives, like your children’s children. Your grandchildren’s children are your first cousins once removed because they share your parents, but a generation separates you.
To determine the relationship between you and your cousin, look at your family trees to find the common ancestor. Then, use a cousin chart to figure out your relationship. For example, Emily and Clayton are distant cousins because they share 3rd great-grandmother, Anne and Stewart’s parents, Judy and Flem. To calculate their cousinhood, they must determine the number of generations separating them from Anne and Stewart’s parents. It is two generations, so they are both second cousins once removed.
Look at Your Grandparents
Understanding terms like “first cousin once removed” can be confusing when it comes to family trees. But, as we dig deeper into our family connections, those once-removed relatives can make for some of the most intriguing discoveries!
A first cousin is someone who shares grandparents with you. If your first cousin has children, those children are your “first cousins once removed” because they are in your generation. However, if that first cousin’s child has children, they are your “first cousins twice removed” because there are two generations between you and the common ancestor.
“Removed” is determined by counting the generations between you and your most recent common ancestor on either the mother’s or father’s side. This number is then multiplied by the relationship label.
So, if you have a first cousin who has a child, that child is your “first cousin once removed” because they are in the same generation as your parents. Then, if that first cousin’s child does the same, those children are your “first cousins once removed” because they share the same grandparents as you and your parents. This continues as you get further away from your ancestor. For example, if your first cousin’s child has a child who is your second cousin once removed, you are your second cousin once removed because they share your great-grandparents with you.
Look at Your Great-Grandparents
Figure out your cousin’s relationship by counting back through generations to find common ancestors. First cousins share parents; second cousins share grandparents, and so on. The number you subtract from the number of generations you and your cousin count back is the relationship label.
The ‘once removed’ part of the designation means that your cousin is one generation above or below you on the generational ladder. You and your cousin are in the same generation as your children, so you’re either first cousins once removed or both first cousins twice removed. However, your cousin is also in the same generation as the grandchild of your first cousin, so you could be both first cousins’ siblings’ grandchildren or your first cousin’s great-grandchildren.
It gets trickier as you move up through the generations to your more distant relatives. When you get to third cousins and beyond, add another “great” before the previous number to figure out your relative’s generational difference. So, a third cousin once removed is the child of your first cousin, and a third cousin twice removed is your second cousin’s child. Each time you add a great, you move up by one generation. The percentage of DNA you and your cousin share decreases as the distance between you increases, so that by fifth cousins, you may only share a small fraction of your autosomal DNA, according to this DNA Wiki article.
Look at Your Great-Great-Grandparents
As you continue to trace your family tree, you will start encountering more and more kinship terms like “first cousin once removed.” These terms communicate how close or distant two people share blood relations. They’re based on counting generations and looking at the common grandparents of each person to determine their relationship. The more common grandparents the shared relatives have, the closer they are.
For example, a first cousin is someone with whom you share one or more of the same parents. A first cousin once removed is a first cousin who is not a sibling but is the child of your parent’s brother or sister or their child.
A second cousin shares one or more of the same great-grandparents with you. A second cousin, once removed, is the child of your first or second cousin and can also be the child of their children (first or second) or their siblings.
As you work through these relationships, you may use the following trick. Count how many “greats” are in the common ancestor and add 1. This will tell you what type of cousin your relative is. Note that there are exceptions to this rule; for example, your 3x great-grandmother might be a niece or nephew of your 1st cousin once removed, so you would need to go back an additional generation to get to a common great-grandparent.
