Counting Cousins: How California Law Figures Out How "Related" You Are

If someone dies without a will, California law has to figure out who inherits — and that often comes down to who counts as the closest relative. But "closest relative" isn't just a feeling. California actually has a math formula for it, written into Probate Code section 13. Here's how it works, explained simply.

Why Does the Law Even Need to Measure This?

When a person dies without a will (or when other relatives need to be identified for a legal case), the law often has to rank relatives by how closely related they are. A child is obviously closer than a second cousin. But what about a niece compared to a great-grandchild? Or an aunt compared to a grandchild?

To answer questions like that fairly and consistently, California law uses a counting system instead of guesswork. This system is called "degree of kinship" or "degree of consanguinity." Consanguinity is just a fancy word for "related by blood."

The Basic Idea: Count the Steps

Think of a family tree like a ladder. Every step up or down that ladder — from parent to child, or child to parent — counts as one "generation." The law calls each generation a "degree." To find out how related two people are, you literally count the number of steps between them on the family tree.

There are two different ways to count, depending on whether one person is a direct ancestor of the other, or whether they're related through a shared ancestor instead.

Type 1: Lineal Kinship (Direct Line)

Lineal kinship is the relationship between two people when one of them is a direct descendant of the other — think parent and child, or grandparent and grandchild. It's a straight line up or down the family tree.

To count the degree, you count the number of generations between the two people. Here's the trick: you don't count the first person, but you do count the second person.

Some examples:

• Parent and child = 1 step apart = 1st degree

• Grandparent and grandchild = 2 steps apart = 2nd degree

• Great-grandparent and great-grandchild = 3 steps apart = 3rd degree

The pattern is simple: every time you add a "great" to the relationship, you add one more degree.

Type 2: Collateral Kinship (Branching Off)

Collateral kinship is different. This is the relationship between two people who share a common ancestor, but neither one is a direct descendant of the other. Siblings are the easiest example — you and your brother or sister aren't each other's parent or child, but you share the same parents.

To count collateral kinship, you do two things: count the steps from the first person up to the shared ancestor, then count the steps from that shared ancestor back down to the second person. Add those two numbers together. Just like before, you don't count the starting person, but you do count the ending person — and you only count the shared ancestor once, not twice.

Some examples:

• Siblings: You go up 1 step to your shared parent, then down 1 step to your sibling. 1 + 1 = 2nd degree.

• Aunt/uncle and niece/nephew: You go up 2 steps to the shared grandparent, then down 1 step to the niece or nephew. 2 + 1 = 3rd degree.

• First cousins: You go up 2 steps to the shared grandparent, then down 2 steps to your cousin. 2 + 2 = 4th degree.

Notice that the further out the relationship, the higher the degree number. A higher number means a more distant relative.

A Quick Cheat Sheet

Relationship	Type	Degree
Parent / child	Lineal	1st
Grandparent / grandchild	Lineal	2nd
Great-grandparent / great-grandchild	Lineal	3rd
Siblings	Collateral	2nd
Aunt or uncle / niece or nephew	Collateral	3rd
First cousins	Collateral	4th

Why This Actually Matters

This isn't just a trivia rule. California's intestate succession laws — the rules that decide who inherits when someone dies without a will — often rely directly on degree of kinship to rank which relatives get priority. So does the law in other situations, like determining who can serve as an estate representative when several relatives have an equal or competing claim, or who counts as an "heir" for notice purposes in a probate case.

In short: when California law needs to settle who counts as the closest living relative, it doesn't leave it to opinion. It counts the steps on the family tree — and section 13 is the rulebook for how to count them.

This post explains the general framework of Probate Code section 13 and is provided for general informational purposes only. It does not constitute legal advice and does not create an attorney-client relationship.