Is It Illegal to Marry Your Cousin in Montana? Here’s What the Law Says

The topic of cousin marriage has sparked discussion and debate for centuries, often intertwined with social norms, religious beliefs, and concerns about potential genetic implications. While cousin marriage might seem unusual in some cultures, it’s far less taboo in others. The laws around first-cousin unions vary widely across the globe, and even within the United States, each state has its own stance on the matter. In this article, we delve into the specifics of cousin marriage laws in Montana, examining the reasons behind potential restrictions and the ongoing debate surrounding this complex issue.

Cousin Marriage Laws in the United States

The United States exhibits a patchwork of laws regarding cousin marriage. Currently, about half of all states explicitly ban first-cousin marriages. Several other states permit cousin marriage with specific stipulations, such as requirements for genetic counseling or the individuals being beyond a certain age. A smaller number of states have no restrictions on cousin marriages.

The Law in Montana

Montana stands as one of the states where first-cousin marriage is fully legal. The relevant Montana statute (Montana Code Annotated 40-1-401) states that marriages between “first cousins or persons of nearer kin” are explicitly prohibited. This means that in Montana, individuals are free to marry their first cousins without any additional legal or medical requirements.

Reasons for Restrictions on Cousin Marriage

The primary arguments against cousin marriage generally fall into two categories:

  • Genetic Concerns: Closely related individuals have a higher chance of sharing recessive genes that can cause harmful health conditions. Children born from cousin marriages might face an increased risk of genetic disorders compared to children of unrelated parents.
  • Social and Moral Concerns: Some people object to cousin marriage based on beliefs about preserving traditional family structures and social norms. There might be concerns about blurring family roles and potential power imbalances within such unions.
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Arguments in Support of Cousin Marriage

Proponents of cousin marriage often put forward the following arguments:

  • Personal Liberty: Supporters emphasize the right of consenting adults to make their own choices about their relationships and family structures. They believe that the government should not interfere with personal decisions when no harm is done to others.
  • Cultural & Historical Precedents: Many cultures throughout history have practiced cousin marriage with varying degrees of acceptance. From ancient royalty to certain present-day societies, examples of cousin unions exist, sometimes as a way to consolidate wealth or social standing.

The Ongoing Debate

The issue of cousin marriage is far from settled. Public opinion is evolving, particularly as understanding of genetic risks continues to develop. While concerns about health risks remain valid, they are often balanced against arguments for personal autonomy and against what is seen by some as unnecessary government intrusion into individual choice.


In Montana, the law is clear: first-cousin marriages are legal. Whether to enter into such a union is a deeply personal decision that potential couples should make after careful consideration and, likely, professional consultation about potential health concerns. The debate surrounding cousin marriage is likely to continue, reflecting our society’s ongoing efforts to balance tradition, genetic science, and individual freedom.

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