Understanding Cousins
Ask most people to explain the difference between a second cousin and a cousin once removed and you will likely be met with a puzzled look. The terminology is genuinely confusing — but once you understand the logic behind it, it clicks into place surprisingly quickly.
The Basic Rule
The key to understanding cousin relationships is to find the most recent common ancestor — the person or couple from whom both people descend.
- First cousins share a set of grandparents
- Second cousins share a set of great-grandparents
- Third cousins share a set of great-great-grandparents
And so on. The number before the word cousin tells you how many generations back the shared ancestor is, minus one.
What Does "Removed" Mean?
"Removed" refers to a difference in generation between two cousins. If you and another person are from different generations — say you are the child of first cousins — then you are first cousins once removed. Two generations apart would make you first cousins twice removed.
Removed simply means: we would be first (or second, or third) cousins if we were in the same generation, but we are not.
A Cousin Relationship Table
The table below shows how relationships are named depending on the shared ancestor and the generation of each person. Find the shared ancestor in the left column, then read across.
| Shared Ancestor | Your generation | Their generation | Relationship |
|---|---|---|---|
| Grandparents | Grandchild | Grandchild | First cousins |
| Great-grandparents | Great-grandchild | Great-grandchild | Second cousins |
| Great-great-grandparents | 2× great-grandchild | 2× great-grandchild | Third cousins |
| Grandparents | Grandchild | Great-grandchild | First cousins once removed |
| Grandparents | Grandchild | 2× great-grandchild | First cousins twice removed |
| Great-grandparents | Great-grandchild | 2× great-grandchild | Second cousins once removed |
A Family Example
Bob Renals and Jack Renals were brothers — not cousins. But their children would have been first cousins to one another. Bob's sons Edwin John and Roy Frederick would have been first cousins to Jack's children.
Edwin John's children and Roy Frederick's children would also be first cousins to each other — they share the same grandparents, Bob and Charlotte Renals.
Now consider the next generation down. Edwin John's grandchildren and Roy Frederick's grandchildren would be second cousins — they share Bob and Charlotte as great-grandparents.
This is why, as a family grows across the generations, the number of cousins multiplies rapidly — and why tracing those connections back to a common ancestor is at the heart of family history research.
Why Do We Have So Many Cousins?
The short answer is: because each generation branches. Two siblings each have children, and those children have children, and so on. Within just four or five generations a single couple can have dozens of living descendants — all of whom are cousins of one another to varying degrees.
Add to this the tendency in earlier centuries for families to remain in the same area and marry within the same community, and you find that in tight-knit places like rural Cornwall and Devon, many people were connected to their neighbours by blood as well as by geography. It is not uncommon in this family history to find the same surnames appearing repeatedly across different branches — Orchard, Facey, Clemens — a reminder of just how interconnected these communities were.