Lawyer Blogger

What States is It Legal to Marry Your Sister

Around the world, sibling marriages are a taboo topic. But in this article, we’ll discuss countries where one can marry their sister — or other family members, for that matter. We’ll also try to shed light on the conflicts, complexities, and subjects surrounding such relationships. Read on!

Sibling Marriages in the US

Siblings can’t get legally married in most places, including the US, though cousin marriages are legal in many countries. Some US states allow people to marry their cousins in some circumstances. These states are:

  • Alabama
  • Alaska
  • Arizona
  • Arkansas
  • California
  • Colorado
  • Connecticut
  • District of Columbia
  • Florida
  • Georgia
  • Hawaii

Some states like Arizona prohibit sibling marriage except when both parties are over 65 years old or at least one of them is infertile. The reason: the risk of generic disorders in their child increases when one marries a sibling.

In Maine, if you want to marry your first cousin, you have to meet with a geneticist or a genetic counselor. You must provide proof of genetic makeup to minimize the risk of having children with genetic disorders.

Similar to Arizona, one can marry their first cousin in Wisconsin as long as the woman is at least 55 or one of them is permanently sterile. In Indiana, you can only marry your first cousin if both of you are 65 or older.

Moreover, many states have punishments for sexual relationships between siblings. In Oklahoma, for instance, such relations are punishable with prison sentences. In New Jersey and Rhode Island, it’s not a crime for siblings to have consensual sexual relationships, but they still can’t get married.

In Other Parts of the World

Avunculate marriage — or marriage with a sibling’s child or parent’s sibling — is legal in many places. However, sexual relations or marriage between siblings is universally considered as incestuous.

In Spain

In Spain, intimate relationships with family members aren’t considered illegal or punishable by law. Family members can marry each other as long as they’re not members up to a third-degree of collateral kinship. For instance, aunts or uncles can’t marry their nieces or nephews.

In Portugal

Portugal also doesn’t punish intimate relationships with family members. However, unlike in Spain, marriage is prohibited up to the second degree of kinship. For instance, marriage between siblings isn’t allowed, but marriage between an uncle or aunt with their nephew or niece is allowed.

In France

In France, marriage is allowed as long as it obtains a presidential order and as long as it meets specific requirements, which is that the person with whom they had a previous relationship has died.

China, Japan, and Russia

In countries like China, Japan, and Russia, sex between family members isn’t prohibited. However, when it comes to marriage, they implement some restrictions. Marriage between first cousins was generally allowed during China’s dynastic era; Japan prohibits marriage between lineal and collateral relatives.


In Sweden, half-siblings can marry each other as long as they have a father in common. They also need to obtain special permission from the government to formalize the marriage.


In the Netherlands, intimate relations between family members aren’t punishable. However, marriage isn’t allowed between adoptive brothers or sisters who have blood ties.


In Brazil and other parts of Latin America, intimate relationships between family members aren’t punishable by law as long as it’s not with someone under the age of 16. If that’s the case, the relationship is heavily punished.


Australia is among the countries that punish intimate relationships between family members; incestuous relationships are punishable by 20 years in prison.

More on Sibling Marriages

Intimate relationships with family members aren’t anything new. Ancient civilizations accepted or at least tolerated the practice until it began to be punished by Roman law. The punishment was to protect the base of society and families. Since then, intimate relations with siblings and other family members have become taboo.

And as mentioned, the children of siblings that marry each other are at risk of genetic disorders due to mutation. Individuals become less fertile and reproduce less.

Exogamy is also an explanation. In primitive tribes, younger people looked for partners outside of their group. In some societies, women left their groups in search of a partner. In others, the men did. These marital ties favored alliances with other families, reducing the possibility of war or confrontations between two tribes. At the same time, primitive cultures also seem to know the genetic issues that may arise out of taboo relationships.

Moreover, in many families where intimacy occurs with members, the relationships aren’t always consensual. In countries where incest is prohibited, the victim feels discouraged to report the situation since they’d also have committed a crime.

Meanwhile, in countries where intimate relationships with family members are not punished, the victim usually reports the situation because they know they haven’t committed any illegal activity. With these in mind, it’s important that such situations are investigated properly so victims of non-consensual incestuous relations are protected.

How Common are Sibling Sexual Relations

The concept of brothers and sisters experimenting in terms of sexual relations is extremely taboo in many societies and cultures. Nonetheless, this doesn’t mean that it’s uncommon for brothers and sisters to experiment.

The Westermarck impact suggests that people who lived together through their formative years become desensitized to each other when it comes to intimate attraction. With this in mind, it’s understandable that kin members who’ve been separated at birth may feel attraction towards each other since they’ve lived away from each other.

Additionally, some siblings experiment when they only meet once in a while. This is common among children whose parents aren’t the same (step-brothers and sisters). According to a study, 10% of males and 15% of females had been involved in or experienced intimate contact with a sibling.

Parents concerned about siblings who experiment with each other in an intimate manner should know that they often do this to understand intimacy — not necessarily because they’re attracted to each other.

As a result, it’s the parent’s job to help children understand what intimate attraction and intimacy are and the gravity of their effects. This way, they can avoid engaging in relationships that may permanently change their lives.

Leave a Reply

Your email address will not be published. Required fields are marked *

Recent Posts