Created with Microsoft PhotoDraw 2000 v2

A handy rule (Rule 1):

*n*th
cousins share a gg...g [*n* times] parent.

For example, 1st cousins share a gparent [grandparent]; 2nd cousins share a ggparent [great-grandparent]; 3rd cousins share a gggparent [great-great-grandparent]; etc. Another way to say the same thing uses an exponent to indicate the repetition count of the "g"s (Rule 1 again):

*n*th
cousins share a g^{n}parent.

Another handy rule (Rule 2):

You are *n*+1 generations
removed from your g^{n}parent.

That is: Your generation count is 1 more than your "g" count. This is easy to see: You are 2 generations removed from any grandparent (gparent, with 1 "g").

A handy algorithm (that uses only Rule 1):

If you know that you, say Joe, have a g^{n}parent
in common with someone's, say Mary's, g* ^{m}*parent, then you can
compute the relationship of Joe to Mary this way: (I should also say that this
assumes there is no

1. Assume *n* > *m*. You can always reverse the
roles if this is not true. If *n* = *m*, then just use Rule 1 above:
Joe and Mary are *m*th cousins (or equivalently, *n*th cousins).

2. Find someone in Joe's line in the same generation as Mary.
Let's say it is Sally (it doesn't matter who it is). Use the formula above to
compute cousinhood: Sally and Mary are *m*th cousins. The short form of
this step is, simply:

The first half of your answer
is "*m*th cousin ..." (where *m*, recall, is the smaller of *m*
and *n*).

3. Now determine how many generations separate Joe and Sally.
Suppose it is *p* generations. Then Joe is Sally's *m*th cousin, *p*
removed. The short form of this step is, simply:

The second half of your answer
is "... *p* removed" (where *p* is *n* - *m*).

An exercise (that uses both Rule 1 and Rule 2):

I met a relative recently who was 5 generations down from our nearest common ancestor, and I was 8 generations down from the same ancestor. The relative's name was Lydia [not her real name]. "What is our relationship?" she asked.

Here's how I computed it. First I determined *m* and *
n*. They are not 5 and 8 as you might first assume. The generation count is
not the same as the number of "g"s in front of "parent". Here's where you
use Rule 2. So my g^{7}parent is in common with Lydia's g^{4}parent.
So some direct ancestor of mine in the 5th generation with Lydia is her 4th
cousin. It doesn't matter who that person is. Determining *p* (the
"remove") is a snap. It's just 8 - 5 (or 7 - 4) equals 3. *p* is just the
difference in generations between Lydia and me. So she and I are 4th cousins, 3
removed (or "3 times removed", or "thrice removed").