Can Cousins with the Same Last Name Get Married? Health Risks Explained

Can people with the same surname get married?

Can people with the same last name get married? Will the babies they have be at risk for abnormal diseases?

Ya-Hui, 10~19 year old female. Ask Date: 2002/09/20

Dr. Wu Zongcheng reply Obstetrics and Gynecology

Consanguineous marriages are considered detrimental in the field of genetics and genetic counseling; they can lead to the expression of recessive genetic disorders.
Therefore, it is advisable for blood relatives, such as first cousins, to avoid marrying each other.
As for individuals with the same surname, it is more challenging to draw conclusions about their genetic relationship—perhaps they share a common ancestor from 500 years ago, or they may have closer blood ties from recent generations.
It is best for individuals with closer genetic relationships to refrain from marrying.

Reply Date: 2002/09/20

More Info

When it comes to the question of whether cousins with the same last name can get married, the answer largely depends on the laws and cultural norms of the specific region or country in which they reside. In many places, including the United States, first cousins are generally allowed to marry, although some states may have restrictions or require genetic counseling. The same applies to cousins who share the same last name; as long as they are not closely related (like siblings or parents), they can typically marry without legal issues.

From a genetic perspective, the primary concern with cousin marriages is the potential for inherited genetic disorders in offspring. When two individuals who are closely related have children, there is an increased risk of recessive genetic disorders manifesting in their offspring. This is because both parents may carry the same recessive gene for a particular condition, which could lead to the child inheriting two copies of that gene (one from each parent), resulting in the expression of the disorder.

However, the risk of genetic disorders is not solely determined by the last name or the fact that the individuals are cousins. It is more about the degree of genetic relatedness. First cousins share about 12.5% of their genes, which is a relatively low percentage compared to siblings, who share about 50%. The risk of genetic disorders in children of first cousins is estimated to be about 1.7 to 2.8 times higher than that of the general population, which means that while there is an increased risk, it is not overwhelmingly high.

For more distant cousins, such as second or third cousins, the risk of genetic disorders is significantly lower and often comparable to that of the general population. In fact, many people are unaware of their distant cousin relationships, and such unions are quite common without any significant health implications.

If individuals are concerned about the potential health risks associated with marrying a cousin, genetic counseling can be a valuable resource. Genetic counselors can provide information about family history, assess the risk of genetic disorders, and discuss options for testing and family planning. This can help prospective parents make informed decisions about their reproductive health.

In summary, cousins with the same last name can generally marry, and while there is a slightly increased risk of genetic disorders in their children, the actual risk is relatively low, especially for more distant cousins. Genetic counseling can provide further insights and help mitigate any potential risks. It is essential to consider both the legal and health aspects when making decisions about marriage and family planning in such situations.

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