In circumstances such as will probates and marriages, it is important to know how to determine degrees of family relationship, because this often determines how the law is applied. For example, in most states, people who are related within 4 degrees of each other may not marry; also, in cases where a person dies without a will, his estate will pass to the closest relation. Calculating degrees of relationship is very simple once you understand the difference between direct relatives -- family members in the same line such as children, parents, grandparents -- and collateral relatives such as cousins, aunts and uncles.
Learn how to count the number of degrees between yourself and relatives in your direct line. Start with yourself as "0" and add 1 degree for each relative in your direct line to determine how many degrees apart you are from direct relatives -- such as parents, grandparents, and children. For example, you are usually related to your mother in the first degree, your grandmother in the second degree, and your great-grandmother in the third degree.
To determine the degrees of relation to a collateral relative (someone not in the direct line), count back to the first relative that you and the collateral relative are both directly related to. For instance, if you are counting the degrees of relation between yourself and a maternal cousin, your maternal grandparent would be in each of your direct lines.
Add the number of degrees that it takes to count up the line to that direct relative, starting with yourself, and then back down the line to the cousin. So, in the example, a first cousin would be a relative in the 4th degree of relationship because you share a grandmother in common, to whom you are both related in the 2nd degree.