Classification of cousins is often misunderstood by non-genealogists. All cousins share a common ancestor, often called the Most Recent Common Ancestor (MRCA). First cousins share common grandparents. Second cousins share common great grandparents. Third cousins share common 2nd great grandparents, and so forth. Skillmans in America who have to date tested their Y-chromosome DNA are all descended from common 6th great grandparents, making all of us 7th cousins.
The son or daughter of your aunt and uncle is your first cousin because you share a common set of grandparents. But what about a child of your first cousin? Most people think that child is their second cousin, but that is not correct. That child is still a first cousin, but “once removed” by the generational difference. So that child is a first cousin, once removed. If that child then had a child of his or her own, you and the younger child would then be first cousins, twice removed, because there are two generations difference between you and the younger child. Your child and your first cousin’s child would be second cousins, because they share common great grandparents.
First Cousins Once Removed
First Cousins Twice Removed
Most genealogical software today has a ‘relationship finder,” in which you can compare any two people in your database and determine how they are related. Nevertheless, a basic understanding of the principles of relationships will make it easy to assess the degrees and removals in the relationships between cousins. At least you now know that your first cousin’s child is not your second cousin.
John E. Skillman III