Genealogy Basics

Cousins, "Removed" and In-Laws: How Family Relationships Are Named

By Monte Horton · October 29, 2026

Sooner or later, every family historian is asked, "So what does that make us?" Here's how to answer it.

Cousins share a common ancestor

Cousins are people who share an ancestor but descend through different children. The number tells you how far back that shared ancestor is:

Each step back adds one to the cousin number.

What "removed" means

"Removed" means you and your cousin are from different generations.

• Your parent's first cousin is your first cousin once removed. (They're first cousins with your parent; you're one generation down.)
• Your grandparent's first cousin is your first cousin twice removed.
• Your first cousin's child is also your first cousin once removed, looking the other direction.

The number of times "removed" is simply the number of generations between you.

A quick way to work it out

1. Find the shared ancestor.
2. Count the generations from that ancestor down to each of you.
3. If the counts are the same, subtract one to get the cousin number: two generations each (grandchildren) means first cousins; three each means second cousins.
4. If the counts differ, take the smaller count and subtract one for the cousin number. The difference between the counts is how many times removed.

Example: your great-grandfather is the shared ancestor. You're 3 generations down from him; your mother's cousin Ruth is 2 generations down. The smaller count is 2, and 2 minus 1 makes you first cousins; the difference, 1, makes you once removed. Ruth is your first cousin once removed.

Other relationships that confuse people

• Half relationships. Half-siblings share one parent. Their children are half first cousins, and they share less DNA than full cousins.
• Double cousins. When two siblings marry two siblings from another family, their children are double first cousins, related through both parents.
• In-laws. Relatives by marriage, not by blood: your spouse's family, and your siblings' spouses. A cousin's spouse isn't your cousin, though most families call them one anyway.
• "Aunt" and "uncle" as titles. Older records and family stories often called a close family friend or an older cousin "Aunt" or "Uncle." Check before adding them to a tree.
• Grand vs. great. Your grandparent's brother is your great-uncle (sometimes called grand-uncle). Both terms are in common use.

Why it matters for research

DNA match lists suggest relationships like "2nd–3rd cousin." Knowing what that means tells you how far back to look for the shared ancestor: great-grandparents to great-great-grandparents. That narrows the search from hundreds of people to a handful of couples.

Put names to the faces

Cousins are often the ones holding the other half of the family's photos. When you find a new cousin, ask what pictures they have, and share yours.