Whether you can have sex with your cousin depends on your state and how closely you’re related. For adult first cousins, the relationship is legal in most of the United States. Only about nine states include first cousins in their criminal incest statutes, and in those places any sexual contact between first cousins can be prosecuted. Everywhere else, two consenting adult first cousins face no criminal exposure, even in states that refuse to let them marry. For second cousins and more distant relations, the relationship is legal essentially everywhere.
The States Where It Is a Crime
Roughly nine states treat sex between first cousins as criminal incest. In those jurisdictions, the offense typically falls under the state’s incest statute, and the classification ranges from a high-level misdemeanor to a serious felony depending on where you are. Felony-level incest charges in the harshest states can carry prison sentences of up to ten years and fines of $10,000 or more. Misdemeanor classifications still bring possible jail time and a permanent criminal record.
Penalties climb higher when other factors are present. A significant age gap between the parties, one person holding a position of authority or trust over the other, or the involvement of a minor can all trigger enhancements. In cases involving a minor, separate charges such as sexual assault of a minor may apply on top of the incest count and carry substantially longer sentences on their own.
The list of states that criminalize first-cousin sex is short and specific. Because these statutes name the covered relationships explicitly, whether your relationship is a crime is a yes-or-no question answered by reading your state’s incest statute or asking a local attorney. Assume nothing based on what a neighboring state does.
Legal to Sleep Together, Illegal to Marry
People often assume that a state banning first-cousin marriage must also criminalize sex between first cousins. Usually it doesn’t. Marriage law and criminal law run on separate tracks, and the great majority of states that prohibit cousin marriage do not treat the sexual relationship itself as a crime. In those places, an adult first-cousin couple can be intimate without breaking any law. They simply cannot get a marriage license.
About twenty-five states prohibit first-cousin marriage entirely, and in most of them such a marriage is considered void, meaning it was never legally valid in the first place. Another twenty states plus the District of Columbia allow first cousins to marry with no restrictions. The remaining states occupy a middle ground, permitting first-cousin marriage only when specific conditions are met. The most common conditions are that both partners be above a certain age (typically 50 or 65), that at least one partner document an inability to have children, or that the couple complete genetic counseling before a license issues.
This disconnect matters more than it first appears. A couple whose sexual relationship is perfectly legal in their state may still have no path to marital tax filing, inheritance rights, or healthcare decision-making authority. Legal intimacy and legal marriage are not the same question, and answering one does not answer the other.
Half-Cousins and Cousins Once Removed
Half-first cousins share only one grandparent instead of two, which cuts the genetic overlap roughly in half compared with full first cousins. Most states that restrict first-cousin relationships do not distinguish between half-blood and whole-blood relatives. If your parent and your cousin’s parent are half-siblings, you’re generally still treated as first cousins under both incest and marriage statutes.
First cousins once removed (your parent’s first cousin, or your first cousin’s child) share about 6.25 percent of their DNA. These relationships sit in a legal gray area. Some states that ban first-cousin marriage are silent on cousins once removed, while others sweep them into the same prohibition. The safest working assumption is that any state restricting first-cousin unions may also restrict first-cousin-once-removed unions. This is one of the situations where checking the specific statute in your state, or asking a family law attorney, is worth the effort.
Second Cousins and More Distant Relations
Second cousins share great-grandparents rather than grandparents, which works out to roughly 3 percent shared DNA. Almost no state restricts sexual relations or marriage between second cousins. At least one state bars marriage between persons closer than second cousins by blood, and depending on interpretation that statute could reach second cousins themselves, but the restriction is extremely rare and second-cousin relationships face no legal barriers essentially anywhere in the country.
For third cousins and beyond, the picture is completely clear. No U.S. jurisdiction restricts these relationships in any way. Shared genetic material at third-cousin distance drops below 1 percent, and for both legal and medical purposes these individuals are treated as unrelated.
Crossing State Lines to Marry
Because the criminal and marriage rules split apart, the natural next question for a first-cousin couple in a marriage-ban state is whether they can travel somewhere permissive, marry there, and come home married. The answer is uncertain and depends on your home state.
Several states have marriage evasion provisions written specifically to block this strategy. Under those laws, if residents leave the state to marry in a way that would be prohibited at home, the marriage is treated as void when they return. That means no joint tax filing, no spousal medical decision-making, and no spousal inheritance under state law. Not every state has an evasion statute, and some existing ones have been narrowed by court decisions, but the risk is real.
Even without an explicit evasion law, recognition is not guaranteed. A state can refuse to honor an out-of-state marriage on general public-policy grounds, and this refusal is more likely where the home state’s own statute declares cousin marriages void rather than merely voidable. Most states that ban cousin marriage use the void classification, which makes out-of-state recognition an uphill fight. Any couple planning this route should talk to a family law attorney in their home state before making travel arrangements.
How to Get a Definitive Answer for Your Situation
The short version: pull up your state’s incest statute and read who it lists. If first cousins aren’t named, consensual adult intimacy is not a crime there. If they are named, it is. For marriage, check your state’s marriage code separately, because the answer will often be different. And if your relationship involves half-cousins, cousins once removed, or a planned out-of-state wedding, a short consultation with a family law attorney licensed in your state is the only reliable way to know exactly where you stand.