In almost every U.S. state, it is not legal to marry your niece. The marriage is treated as void from the beginning, meaning it never legally existed, even if a license was issued and a ceremony took place. Two states carve out narrow exceptions, and in most states the sexual relationship itself is a felony. The details of your state’s statute, and of your family relationship, decide whether any exception could possibly apply.
The Nearly Universal Ban
Uncle-niece marriages appear on the list of prohibited degrees of kinship in nearly every state’s family or domestic relations code. California’s family code names marriages between uncles or aunts and nieces or nephews as “incestuous, and void from the beginning, whether the relationship is legitimate or illegitimate.” Texas voids marriage between a person and a parent’s sibling or a sibling’s child, whether related by whole blood, half blood, or adoption.
“Void from the beginning” is the phrase to focus on. A void marriage is not a marriage that a court has to undo. It is treated as though it never happened, so no annulment is required to end it, and the parties generally have no rights as spouses: no marital property to divide, no spousal support, no automatic inheritance as a surviving spouse. A couple who held a ceremony, bought a house together, and lived as married for years can discover during a divorce, probate case, or immigration review that none of it counted.
The Two Narrow Exceptions
New York: Half-Blood Only
New York’s Domestic Relations Law lists marriages between an uncle and niece or an aunt and nephew as incestuous and void. A full-blood uncle-niece marriage is just as illegal there as anywhere else.
In 2014, the New York Court of Appeals interpreted that statute narrowly and ruled that a marriage between a half-uncle and a half-niece does not fall within the prohibition. The court read “uncle and niece” to mean relationships of the whole blood only.1Justia Law. Nguyen v Holder – 2014 – New York Court of Appeals Decisions So in New York, if you share only one parent with your sibling, and that sibling has a child, you can legally marry that child. If you share both parents with your sibling, you cannot. This exception is specific to half-blood relationships running through a half-sibling, and it exists in no other state.
Rhode Island: Jewish Religious Solemnization
Rhode Island’s statute exempts marriages “solemnized among the Jewish people, within the degrees of affinity or consanguinity allowed by their religion” from the state’s general prohibitions on marriages between close relatives. Because Jewish religious law has historically permitted uncle-niece marriages, those unions are protected when performed within the Jewish faith in Rhode Island.2Rhode Island General Assembly. Rhode Island General Laws Title 15 Chapter 15-1 Section 15-1-4 – Marriages of Kindred Allowed by Jewish Religion
This exception is unique in the country. It does not give anyone in Rhode Island a general right to marry a niece or nephew; it applies specifically to marriages solemnized under Jewish religious law.
The Underlying Relationship Is a Felony in Most States
Even where the marriage question looks like a technicality, the sexual relationship between an uncle and niece is itself a crime in most states, regardless of whether both parties are consenting adults.
Kentucky classifies incest between consenting adults as a Class C felony carrying five to ten years in prison, and the statute specifically names uncle, aunt, nephew, and niece.3Kentucky Legislative Research Commission. Kentucky Revised Statutes 530.020 – Incest Maryland imposes one to ten years for sexual intercourse with a person you cannot legally marry, which includes nieces and nephews.4Maryland General Assembly. Maryland Criminal Law Code Section 3-323 – Incest Sentencing ranges vary across the country, but incest charges are nearly always felonies. In New York, where the half-blood exception exists for marriage, solemnizing a prohibited full-blood uncle-niece marriage can bring fines and up to six months in jail for the parties, plus misdemeanor charges for the officiant.
These cases do get prosecuted, often surfacing through divorce filings, immigration petitions, or family disputes.
Traveling to Another State Usually Doesn’t Work
A natural question is whether a couple can simply travel to a state where the marriage might be legal. In practice, this rarely produces a marriage that holds up at home.
States handle out-of-state marriages in two broad ways. Some follow the “place of celebration” rule, recognizing any marriage valid where it was performed. Others follow statutes modeled on the Uniform Marriage Evasion Act, which voids a marriage if the couple left their home state specifically to dodge a prohibition and then returned.5Social Security Administration. POMS GN 00305.155 – The Uniform Marriage Evasion Act
Even in place-of-celebration states, courts have treated uncle-niece marriages as a separate category. A Louisiana court distinguished first-cousin marriages from uncle-niece marriages, pointing out that uncle-niece relationships fall within the state’s criminal incest statute and reflect a qualitatively different level of consanguinity.6FindLaw. Ghassemi v Ghassemi – 2008 – Louisiana Court of Appeal Decisions The realistic expectation is that your home state will not recognize an uncle-niece marriage performed elsewhere.
Half-Blood and Adopted Relatives
If your relationship is through a half-sibling or through adoption rather than full blood, the exact wording of your state’s statute matters.
The trend has been to close gaps around half-blood relationships. Georgia amended its incest statute in 2015 to explicitly include uncle and niece or nephew “of the whole blood or of the half blood” after a court ruling found that the earlier version did not reach half-uncle relationships.7FindLaw. State v Wright – 2026 – Georgia Court of Appeals Decisions Most states that have addressed the question treat half-blood nieces the same as full-blood nieces for marriage purposes. New York is the outlier. Some statutes say “whole or half blood” explicitly; others are silent, and silence has sometimes been read as not covering half-blood ties.
Adoption works differently from state to state. Texas voids marriages between a parent’s sibling and a sibling’s child by adoption just as it does for blood relationships. Other states frame their prohibitions around blood relationships and don’t clearly address adopted nieces. If you were adopted into a family and are considering marrying an uncle or aunt from that family, check whether the statute names adoption specifically.
What a Void Marriage Costs You
Because a void marriage is treated as though it never existed, the parties generally have no claim to marital property division, no spousal support, and no automatic inheritance rights. A few states apply the putative spouse doctrine, which can grant a share of property and limited support to a party who genuinely and reasonably believed the marriage was valid. The doctrine requires good faith; it does not help someone who knew about the prohibition, and it does not make the marriage lawful.
Children born from a void uncle-niece marriage are usually protected. Most states have statutes preserving the legitimacy and inheritance rights of children whose parents entered the marriage in good faith, even if the marriage itself turns out to be void.8Social Security Administration. POMS GN 00306.040 – States With True Void Marriage Statutes Specifics vary: some states extend legitimacy automatically, others require the good-faith element, and a few older statutes are less generous.
Before You Act
Marriage license applications ask about the relationship between the applicants, and lying on the application is a separate offense in most states. A mistakenly issued license does not validate a void marriage. The problem can surface years later during estate proceedings, immigration petitions, or insurance claims.
If you are in this situation and believe one of the narrow exceptions might apply, talk to a family law attorney in your state before anything else. The exceptions are defined with precision, and assuming you qualify without legal advice carries real criminal exposure, the loss of property and inheritance rights, and potential immigration consequences if either party is not a U.S. citizen.