Levels of cousins, also called degrees of cousinship, are fairly tricky to figure out. Especially if you come from a large family, deciding how to determine first, second, and third cousins, and also what once or twice removed means can be difficult. Cousins are not based on the relationship of your parents to siblings, and they’re not based on marriages, except on an informal basis. Instead, you determine levels of cousins based on two people’s common ancestor.

For instance, if your mom’s sister has kids, you might conclude that these children are your first cousins. This would be correct, but the relationship of first cousins is not based on the fact that these are the children of your mom’s sister. Instead, the children of your aunt are your first cousins to you because you share a grandparent in common. This is your common ancestor, to whom you both claim the same relationship. Note that this doesn’t apply for kids of the same parents who share the same grandparent. Instead these children’s closest common ancestors are their parents, so they are siblings, not cousins.

When children share the same great grandparent, but not the same grandparent, they are considered second cousins. So, if you have children, and your first cousin, (your aunt’s child) has children, then these children will have a great grandparent in common. It gets a little more complicated to figure levels of cousins, when you consider your cousin’s children.

When the common ancestor does not have the same relationship to two people, then you get into the whole issue of removals. In the case of your cousin’s children and you, your common ancestor is your grandparent, but to these children, that person is their great grandparent. Therefore your first cousin’s children are your first cousins once removed. Removals occur only when the relationship to the ancestor is separated by generation.

Here are some examples of levels of cousins with removals:

Jane has a grandparent who is the great grandparent of Joey.
Jane and Joey are first cousins once removed.

Jane has a grandparent who is the great, great grandparent of Jim.
They are first cousins twice removed.

Jane has a grandparent who is the great, great, great grandparent of John.
They are first cousins three times removed.

Levels of cousins without removals always mean the common ancestor has the same relationship to each cousin. Examples include:

• First cousins—two people share a grandparent
• Second cousins—two people share a great grandparent
• Third cousins—two people share a great, great, grand parent.

It gets considerably more complicated when determining second or third levels of cousins and degree of removal. If you have a great grandparent who is someone else’s great, great, great grandparent, you are second cousins once removed. If you have a common ancestor of a person who is your great, great, great grandparent and to some else is a great, great, great, great grandparent, you are third cousins once removed. Removal essentially counts generational differences or how many generations you and a person are apart from the common ancestor.

There is one special cousin relationship called double cousins, which makes people doubly related to each other. This occurs when two sisters marry two brothers. The children of these marriages will share not only a common grandparent but will share two sets of grandparents. Hence they are double cousins, and likely to be closely related, from a genetic standpoint, to each other.

Cousinship here is determined from European and American standards. Levels of cousins may be different in other cultures, and the term cousin may not even exist in certain world cultures. It can get a little murky figuring out these relationships, and some people essentially avoid the issue and just call any relatives they know of as cousins or second cousins. From a genealogical standpoint, this isn’t quite correct, but still implies family and relationship.