Is It Illegal to Marry Your Cousin in California? A Complete Guide to State Law

The question of whether marrying one’s cousin is legal often sparks curiosity and debate, touching on a complex intersection of law, culture, and genetics. While many states across the U.S. maintain outright bans or strict restrictions on such unions, the legal landscape in California takes a distinctly different, and often surprising, approach.

For couples who are first cousins and wish to legally bind their relationship, the clear answer in California is: No, it is not illegal. The state explicitly permits marriage between first cousins without any special conditions, placing it among a minority of states with this permissive stance.

This comprehensive guide will delve into the specifics of California law, examine the broader context of cousin marriage in the U.S., explore the historical and cultural underpinnings of these laws, and address the frequently cited genetic and social considerations.

California Law: The Definitive Legal Stance

California’s marriage statutes, primarily contained within the Family Code, clearly outline which familial relationships are prohibited from entering into a legal marriage. These restrictions are rooted in the concept of consanguinity, or relationships by blood, and are primarily designed to prevent incest.

The Clear Allowance for First Cousins

California Family Code $\S 2200$ and $\S 2201$ void marriages within certain degrees of kinship, such as between:

Parents and children (including ancestors and descendants of every degree).
Brothers and sisters (of the half or whole blood).
Uncles/Aunts and Nieces/Nephews.

Crucially, first cousins are not included in this list of prohibited relationships.

A first cousin is defined as the child of one’s aunt or uncle, meaning they share a common set of grandparents.
The relationship is considered four degrees of separation, which falls outside of California’s legally prohibited range for marriage.
As long as both parties meet all other standard legal requirements for marriage—such as being of age (18 or older without parental or court consent), not already married, and of sound mind—their union is fully recognized by the state.

Key Fact: California does not impose any special requirements on first-cousin couples, such as genetic counseling, being above a certain age (e.g., 65), or proof of infertility, as some other permissive states do. The marriage is treated the same as any other legal union.

Distinction from Incest Laws

It is important to distinguish between marriage laws and incest laws, though they often overlap. In California, Penal Code 285 PC defines the crime of incest. While this code prohibits sexual relations or marriage between the closely related individuals listed in the Family Code (parents/children, siblings, aunts/uncles/nieces/nephews), it also explicitly does not include first cousins as a prohibited relationship for sexual relations or marriage.

In short, a marriage between first cousins in California is not considered incestuous under the state’s criminal or family law.

The National Landscape: A Patchwork of Laws

California’s stance on cousin marriage stands in sharp contrast to the laws in roughly half of the other U.S. states, creating a confusing, piecemeal legal map across the country. This divergence reflects a broad cultural and political debate about personal autonomy versus public health concerns.

States that Prohibit Cousin Marriage

According to various legal and sociological reports, approximately 24 states prohibit marriage between first cousins outright, often citing historical, moral, or genetic concerns. Examples of states with blanket bans include Arkansas, Kentucky, and Texas.

States with Conditional Allowances

Another group of states, about eight, allow first-cousin marriage but impose strict conditions, often revolving around the couple’s age or ability to reproduce. For instance:

State	Conditional Requirement for First Cousin Marriage
Arizona	Allowed only if both parties are 65 or older, or if one party is infertile.
Illinois	Allowed only if both parties are 50 or older, or if one party is infertile.
Maine	Requires genetic counseling from a state-approved medical practitioner.
Utah	Allowed only if both parties are 65 or older, or both are 55 or older and one is infertile.

States that Allow Cousin Marriage Without Restriction

California belongs to the group of approximately 18 states that permit first-cousin marriage without any special conditions. Other notable states in this group include:

New York
Maryland
New Jersey
Vermont

The Rule of “Comity” and Out-of-State Marriages

A key legal consideration for first-cousin couples is how their marriage is recognized when they travel or move. The doctrine of comity generally dictates that a marriage validly performed in one state will be recognized in another.

For California Residents: A first-cousin marriage performed in California is valid in the state. If the couple moves to a state that allows cousin marriage, the union remains valid.
The Comity Exception: However, if a California couple moves to a state that explicitly voids all out-of-state cousin marriages (such as Arkansas or Iowa), the validity of their marriage could be challenged, though this is rare and often pertains to marriages that violate strong public policy. The general consensus is that a marriage validly contracted where it took place is usually accepted elsewhere, but legal counsel is always recommended.

Genetics and Public Policy: The Core of the Controversy

The primary and most frequently cited reason for restricting cousin marriage is the concern over the increased genetic risk to offspring. This concern is what drove many states to pass bans starting in the mid-to-late 19th century.

Facts vs. Stigma

When two people are related, their children are more likely to inherit the same recessive genes from both sides, increasing the probability of expressing a genetic disorder. While this is the foundation of the concern, the statistical reality is often exaggerated in public perception.

Type of Union	Background Risk of Birth Defects	Estimated Risk for Offspring	Increase in Risk
Unrelated Parents	N/A	$\approx 3\%$ to $4\%$	N/A
First-Cousin Parents	Above the background risk	$\approx 4\%$ to $7\%$	$\approx 1.7\%$ to $2.8\%$

Statistical Reality: The difference in risk for birth defects between children of unrelated parents and children of first-cousin parents is relatively modest—an increase of roughly 2 to 3 percentage points.
Inbreeding vs. Single Event: The risk significantly escalates only when consanguineous marriages occur over multiple successive generations, a scenario that is not typical in the U.S.

The Ethical Argument in California

California’s non-restrictive policy is often seen as prioritizing personal autonomy and cultural diversity over a marginal public health risk. The argument is two-fold:

Individual Liberty: The decision to marry and reproduce is considered a fundamental right, and the state’s intervention is not justified by the small increase in genetic risk.
Genetic Counseling: Modern medicine allows couples to address this risk through genetic counseling and prenatal testing, empowering them to make informed personal decisions rather than facing a state-mandated ban.

Historical and Cultural Context

The history of cousin marriage is long and varied across cultures, reflecting the practice’s complex social function.

A Global Norm, a Western Taboo

Worldwide, consanguineous marriages—marriages between people who are second cousins or closer—remain common, accounting for an estimated 10% to 20% of all marriages globally, particularly in parts of the Middle East, North Africa, and South Asia. In these cultures, such unions are often seen as preserving family ties, wealth, and cultural values.

In the United States, opposition to cousin marriage rose sharply in the late 19th and early 20th centuries.

Eugenics Movement: The bans passed in the U.S. during this era were heavily influenced by the rise of the eugenics movement, which incorrectly associated cousin marriage with “feeble-mindedness” and hereditary degeneracy, often targeting immigrant groups and the rural poor.
Shifting Social Norms: As industrialization and improved transportation expanded people’s social circles, the need to marry within a small, local pool of family relations diminished, and the practice became a social and legal taboo in many regions.

California, a state defined by its diverse, modern, and libertarian-leaning legal environment, has resisted the trend of blanket prohibition, instead favoring a legal framework that respects individual choice and cultural practices.

Practical Steps and Considerations for First-Cousin Couples

If you and your first cousin are considering marriage in California, the legal path is straightforward, but there are important considerations to address:

1. Fulfill Standard Marriage Requirements

The process is identical to any other marriage:

Obtain a valid marriage license from any County Clerk’s office.
Present valid photo identification.
Pay the required fee (which varies by county).
Have a legal ceremony performed by an authorized officiant.

2. Seek Genetic Counseling

While not legally required by the state, consulting a certified genetic counselor is highly recommended for any consanguineous couple planning to have children. A counselor can:

Assess Risk: Help determine the specific risks based on a detailed family history.
Identify Carriers: Screen for specific recessive genetic disorders prevalent in the family’s shared ancestry.
Discuss Options: Inform the couple about options like prenatal diagnosis or preimplantation genetic diagnosis (PGD).

3. Review Domicile Laws

If you plan to live outside of California, especially in a state with a ban, it is vital to research that state’s laws regarding the recognition of out-of-state cousin marriages. For example, a marriage validly performed in California may still be considered voidable or void if the couple moves to a state like Texas or Iowa, potentially impacting spousal rights, inheritance, and benefits.

Conclusion: A Matter of Personal Autonomy

The question, “Is it illegal to marry your cousin in California?” is met with a firm legal negative. California’s marriage law reflects a contemporary legal philosophy that champions personal autonomy and cultural recognition. By excluding first cousins from the list of prohibited relations, the Golden State trusts adult citizens to make deeply personal relationship and reproductive decisions, a stance backed by modern medical data that diminishes the magnitude of the often-cited genetic risk.

For first-cousin couples in California, the journey to a legally recognized marriage is uncomplicated. However, due diligence, particularly seeking genetic counseling and understanding how your marriage is viewed in other states, remains a crucial step in ensuring a secure and informed future.