Family Tree Terminology

Related by Marriage

The following glossary helps you to understand the terms that describe the family connection that exists between those that are related only through marriage.
Father-in-law — the father of your spouse
Mother-in-law — the mother of your spouse
Son-in-law — the husband of your daughter
Daughter-in-law — the wife of your son
Step-father — your mother's second (or subsequent) husband
Step-mother — your father's second (or subsequent) wife
Step-child (son/daughter) — your spouse's child (son/daughter) from a former marriage
Half-brother/sister — a sibling with whom you share one, but not both parents

Counting Cousins
If you've ever wondered how you are related to your third cousin, here's a brief explanation:
Your first cousins are the people in your family who have two of the same grandparents as you. In other words, they are the children of your aunts and uncles.
Your second cousins are the people in your family who have the same great-grandparents as you, but not the same grandparents.
Your third cousins have the same great-great-grandparents as you.
Your fourth cousins have the same great-great-great-grandparents, and so on.

Removing Relatives
When the word "removed" is used to describe a relationship, it indicates that the two people are from different generations. You and your first cousins are in the same generation (two generations younger than your grandparents), so the word "removed" is not used to describe your relationship.

"Once removed" means that there is a difference of one generation. For example, your mother's first cousin is your first cousin, once removed. This is because your mother's first cousin is one generation younger than your grandparents (remember, cousins are defined by their common relationship to one set of grandparents) and you are two generations younger than your grandparents. This one-generation difference means you are "once removed."

"Twice removed" means that there is a two-generation difference. You are two generations younger than a first cousin of your grandmother, so you and your grandmother's first cousin are "first cousins, twice removed," and so on.