The number associated with your cousin has to do with how many generations away your common ancestor is.
For example:

First cousins

share a

grandparent

(2 generations)

Second cousins

share a

great-grandparent

(3 generations)

Third cousins

share a

great-great-grandparent

(4 generations)

Fourth cousins

share a

3rd-great grandparent

(5 generations)

Count how many "greats" are in your common ancestor's title and add 1 to find out what number cousin your relative is. Note that grandparents have no “greats” in their titles, so cousins who share grandparents are first cousins because 0 + 1 = 1. However, keep in mind that this trick only works if you are both the same number of generations removed from the common ancestor.

Sometimes you and your cousin may share a common ancestor, but you each call this ancestor something different. For example, the common ancestor may be your great-grandparent, but your cousin's great-great grandparent.

This is where the phrase "once removed" comes in handy.

To be a "once removed" from a cousin means you are separated by 1 or more generations.

If you look at the cousin chart above, you’ll see that each row is color-coded by generation. You, your siblings, and your first, second, and third cousins are all of the same generation.

You may have noticed that the boxes labeled "cousin once removed" are either from one generation above or below you. You are "once removed" if you are separated by 1 generation and "twice removed" if you are separated by 2 generations, and so on.

Your parent's first, second, and third cousins are also your first, second, and third cousins—but once removed. This is because your parents and their generation are 1 above yours. Likewise, your grandparents' first, second, and third cousins are also your first, second, and third cousins, this time twice removed. This pattern continues throughout each generation. So, for example, a first cousin once removed is either the child of your first cousin or the parent of your second cousin.

So . . .

William / Agusta Burton McKeever

Relationship	Name	Name	Ancestor
Siblings	Alberta	Fred	Share the same Parents
1st Cousins	Mildred	Marguerite	Share the same Grandparents
2nd Cousins	Mildred's Kids (Alice et al)	Marguerite's Kids (Beverly Jean)	Share the same Great Grandparents
3rd Cousins	Mildred's Kids' Kids (Len et al)	Marguerite's Kids' Kids (Mary Kay et al)	Share the same Great-Great Grandparents

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