Counting cousins—explaining second, third, and fourth cousins.
Figuring out how you’re related to a cousin involves “counting back” through the generations to see how you’re connected. Your parents are one generation back, your grandparents are two generations back, and so on.
First cousins share grandparents, counting back two generations to their shared ancestors.
Second cousins count back three generations to their great-grandparents.
Third cousins count back four generations to their great-great-grandparents.
Sensing a pattern? Subtract one from the number of generations you each count backward, and that tells you your relationship to that cousin.
What does it mean when a cousin is “once removed”?
First cousins, second cousins, and so on belong to the same generation as one another, counting back the same number of generations to their shared ancestors. But if your cousin is a generation older or younger than you, we use the term “removed” cousins.
Imagine that you and your cousin share a relative: it’s your grandfather, but your cousin’s great-grandfather. In other words, you count back two generations to your shared ancestor, but your cousin counts back three. In this case, you would be first cousins once removed, since there is a one-generation difference between you.
What about even more distant cousins?
Putting the two concepts together, we can put a name to any relation in the family tree. Each cousin can be numbered based on how many generations back your shared ancestors are and “removed” a given number of times, based on how many generations apart you are from each other.
One thing to bear in mind when dealing with “removed” cousins is that determining whether you are first, second, or third cousins is a little trickier, since you end up with different numbers when counting back to your common ancestor. In these cases, the number is based on which one of you counts back the fewest number of generations.
For example, if your cousin counts back three generations while you count back five, then you would be second cousins twice removed. The “second” would be due to the number of generations back your cousin counted to a common ancestor, and “twice removed” thanks to the difference in generations between you.
How cousins can help tell your family story.
What’s the benefit of keeping track of all these cousins and how they’re related to you? For one thing, if you are able to connect with your cousins and collaborate on family history research, you each stand to benefit. You all carry different pieces of the family story and working together provides everyone with a richer, fuller understanding of it.
AncestryDNA® can match you with your cousins with a high degree of accuracy with a simple DNA test. You may discover many of your 4th and 5th cousins—and sometimes even your 8th or 10th cousins. In fact, if you and your DNA matches both have family trees connected to your profiles, AncestryDNA can often find your common ancestors for you and tell you exactly how you’re related.