Cousin marriage laws by state fall into three groups: 25 states prohibit first-cousin marriage outright, 18 states and the District of Columbia allow it with no special conditions, and seven states permit it only when couples meet age or fertility requirements. Second cousins and more distant relatives can marry anywhere in the country. Where you live matters, because a marriage that is fully legal in one state may be treated as void, or even criminal, a few hundred miles away.
States That Ban First-Cousin Marriage
Twenty-five states treat first-cousin marriages as void from the start. A license issued by mistake does not save the marriage; the state acts as though the union never existed. Lying on a marriage application to hide the relationship can also expose an applicant to perjury charges, since the form is typically signed under oath.
Some prohibition states go further and criminalize the sexual relationship itself under their incest statutes. Texas classifies intercourse with a first cousin as a third-degree felony under its prohibited sexual conduct statute, and the definition reaches half-blood and adoptive relationships as well.1State of Texas. Texas Penal Code Section 25-02, Prohibited Sexual Conduct A third-degree felony in Texas carries two to ten years in prison and fines up to $10,000.2State of Texas. Texas Penal Code Section 12-34, Third Degree Felony Punishment Other prohibition states stop at declaring the marriage void without separately criminalizing the conduct.
A void marriage has real consequences beyond the piece of paper. Property acquired during the relationship is not automatically marital property. Spousal rights to make medical decisions, inherit without a will, or take a share of an estate may not apply. Employer health coverage carried as a spouse can be reversed. Children, however, are generally protected. Illinois, for example, provides that children born from a prohibited marriage are the lawful children of both parties, and most states have similar protections.3Justia Law. Illinois Compiled Statutes 750 ILCS 5 Part II – Marriage
States That Allow First-Cousin Marriage Without Conditions
Eighteen states and the District of Columbia let first cousins marry the same way any unrelated couple does: apply for a license, meet the ordinary age and identification rules, and go through the standard ceremony. There is no genetic counseling requirement, no age threshold beyond the general marriage age, and no medical certificate involved.
The Seven States With Conditional Rules
Seven states allow first-cousin marriage only when the couple meets specific conditions. Six of the seven aim at preventing biological children from the union, either through age or through proof of sterility. Maine takes a different route and focuses on informed consent.
- Arizona: First cousins may marry if both are at least 65. Younger cousins can marry only with a superior court judge’s approval after proving that one of them cannot reproduce.4Arizona Legislature. Arizona Revised Statutes Title 25 – Section 25-101, Void and Prohibited Marriages
- Illinois: Both parties must be at least 50, or one must file a physician’s certificate stating they are permanently and irreversibly sterile.3Justia Law. Illinois Compiled Statutes 750 ILCS 5 Part II – Marriage
- Indiana: Both cousins must be at least 65.5Indiana General Assembly. Indiana Code 31-11-1-2, Marriage to Close Relative Prohibited
- Maine: First cousins must obtain genetic counseling and submit a physician’s certificate confirming they received it. The certificate is filed with the clerk or state registrar when the couple files their intent to marry.6Maine State Legislature. Maine Code Title 19-A Section 701, Prohibited Marriages and Exceptions
- Minnesota: First-cousin marriages are prohibited except those “permitted by the established customs of aboriginal cultures.” This is the narrowest exception among the seven.7Minnesota Office of the Revisor of Statutes. Minnesota Statutes Section 517.03, Prohibited Civil Marriages
- Utah: First cousins may marry if both are at least 65. If both are at least 55, a district court can approve the marriage after finding that one party cannot reproduce.8Utah Legislature. Utah Code 30-1-1, Incestuous Marriages Void
- Wisconsin: First cousins may marry if the woman has reached age 55, or if either party submits a physician’s affidavit certifying permanent sterility.9Wisconsin State Legislature. Wisconsin Statutes 765.03, Who Shall Not Marry
Second Cousins, Double First Cousins, and Adoption
Marriages between second cousins or more distant relatives are legal in every state. Second cousins share great-grandparents rather than grandparents, and lawmakers do not regulate that degree of relationship. A rough test: if you have to go back three or more generations to find a common ancestor, no state’s cousin rules apply.
Double first cousins are a different story. This happens when two siblings from one family each marry a sibling from another family, and both couples have children. Those children share all four grandparents instead of two, making them genetically closer than ordinary first cousins. North Carolina permits regular first-cousin marriage but specifically bans double first cousins from marrying. If your family tree fits this pattern, check your state’s statute carefully rather than assuming the ordinary first-cousin rule applies.
Adoption also matters. Several states extend their cousin marriage prohibitions to relatives by adoption, not just by blood. The Texas prohibited sexual conduct statute expressly covers adoptive relatives, so cousins related only through adoption face the same restrictions.1State of Texas. Texas Penal Code Section 25-02, Prohibited Sexual Conduct Arizona defines its prohibited relationships by “blood” and does not reference adoption in the same way. Half-blood cousins, who share only one grandparent, are almost always treated the same as whole-blood cousins. Wisconsin, for example, draws its line at anyone “nearer of kin than 2nd cousins” without distinguishing half from whole blood.9Wisconsin State Legislature. Wisconsin Statutes 765.03, Who Shall Not Marry
Moving to a State That Bans Cousin Marriage
A couple who legally marries in a permissive state and then moves to a prohibition state enters uncertain territory. The Constitution’s Full Faith and Credit Clause requires states to respect each other’s judicial proceedings, but the Supreme Court has never held that the clause forces a state to recognize an out-of-state marriage that violates its own public policy. States retain significant discretion. Some will honor a cousin marriage validly performed elsewhere; others will treat it as void once the couple establishes residency.
The practical fallout tracks the void-marriage consequences above: lost spousal rights, disrupted insurance and benefits, and complications when dividing property. Anyone in this situation should look up the destination state’s specific statute before relocating. A valid California marriage does not automatically carry over into Texas.
Federal Recognition of Cousin Marriages
Immigration
For immigration purposes, the federal government follows a “place of celebration” rule. If a marriage was legally valid where it was performed, federal agencies generally recognize it when evaluating visa petitions and green card applications.10U.S. Citizenship and Immigration Services. USCIS Policy Manual Volume 6, Part B, Chapter 6 – Spouses A first-cousin marriage performed in a state that permits it can support a family-based immigration petition even if the couple later lives in a state that bans such unions. State Department guidance tells consular officers to accept a USCIS petition approval rather than reach their own conclusion about validity.11U.S. Department of State. 9 FAM 102.8, Family-Based Relationships The marriage must still meet the general immigration standards: both parties legally free to marry, and no violation of broad U.S. public policy.
Social Security
Social Security treats a void marriage in a particular way. Under agency policy, a remarriage that is “absolutely void” does not terminate entitlement to widow’s or widower’s benefits from a prior marriage.12Social Security Administration. POMS GN 00207.003, How Remarriage Affects Widow(er)’s Benefits Someone already receiving survivor benefits who then enters a cousin marriage their state treats as void generally keeps those benefits, because in the government’s view no valid remarriage happened. The flip side is that a void marriage cannot be used to claim new spousal or survivor benefits.
Taxes After an Annulment
If a court voids your marriage, the IRS requires amended returns for every affected tax year still within the statute of limitations, generally three years from filing or two years from paying the tax, whichever is later.13Internal Revenue Service. Filing Taxes After Divorce or Separation Filing status changes to single, or head of household if you qualify. That shift can produce additional tax, since married-filing-jointly brackets are more favorable for many couples, and it can affect credits and deductions claimed on the original returns.