In Montana, it is illegal to marry your first cousin. The state’s marriage laws explicitly prohibit marriage between first cousins, reflecting concerns about close familial relationships and potential health risks associated with closely related couples having children.
However, Montana does allow marriages between more distant relatives, such as second cousins, and also permits marriage between cousins once removed and half-cousins.
Montana’s legal code lists prohibited marriages that include unions between an ancestor and a descendant, siblings (whether full or half), and first cousins. These restrictions aim to prevent marriages that the state considers too close in family relationship. While first cousins cannot marry in Montana, they are not forbidden from having a consensual relationship or cohabitating, as the legal ban applies specifically to marriage.
Compared to other states, Montana follows the approach of banning first cousin marriages wholesale, with no exceptions for age or genetic counseling, unlike some states that permit cousin marriage under certain conditions. Neighboring states such as Idaho, Wyoming, North Dakota, and South Dakota also do not allow first cousin marriages.
If you are related to someone more distantly, such as a second cousin, marrying in Montana is legally permitted. Couples planning to marry within the state must disclose their relationship on the marriage license application, indicating the nature of any familial ties.
It is advisable for couples who are cousins and considering marriage to consult legal counsel and healthcare professionals to understand the implications fully, especially regarding genetics and health.
Montana law prohibits marriage between first cousins but permits marriage between more distant relatives. This legal framework balances concerns over close genetic relationships with respect for individual freedoms in less closely related unions.
Couples should ensure they understand Montana’s laws and any health considerations before marrying their cousin or a relative within the allowed degree of kinship.
Sources
[1] https://en.wikipedia.org/wiki/Cousin_marriage_law_in_the_United_States
[2] https://collincountymagazine.com/2025/06/30/is-it-illegal-to-marry-your-cousin-in-montana-heres-what-the-law-says/
[3] https://en.wikipedia.org/wiki/Cousin_marriage
[4] https://www.legalmatch.com/law-library/article/cousin-marriage-laws.html
[5] https://dataminingdna.com/can-first-cousins-marry-in-montana/
[6] https://courts.mt.gov/forms/marriage
