Dating first cousin

Dear Alice,

What are the pros and cons (legally and morally) of dating your 1st cousin? To make a long story short, my cousin and I became close friends, then fell in love with each other. We have that "don't care" attitude on what others say or think about our relationship, but are curious anyway.

Jus' need advice from a 3rd party...

Dear Jus' need advice from a 3rd party...,

While there’s sometimes stigma associated with dating within families, anyone can date their first cousin. However, the questions around legality and morality come into play when you start discussing a future including marriage or having children with your partner. Read on for some of the pros and cons of consanguineous relationships, or relationships between two people who descended from the same ancestor.

Consanguinity is most common between first cousins but can be between second and third cousins, as well as double first or second cousins. The legality of these relationships varies by state in the U.S., with some having a range of legal options, legal with certain restrictions, or completely illegal. For example, in Utah, it is illegal to marry your first cousin or any one of a closer relation to you than that on the family tree. But, Utah courts make an exception for couples who are both over 65 years old or if both are over 55 and the court has found that neither partners are able to reproduce. If you’re thinking about marrying or having kids with your partner, it’s a good idea to check the laws in your state.

When it comes to questions of morality, it’s helpful to understand some of the history and cultural context around these kinds of relationships. Until the mid-19th century, cousin marriages were allowed in the U.S. and Europe. In fact, these marriages were even encouraged to keep wealth within the family and were believed to protect against disease-causing parasites (it’s now under question whether offspring from consanguineous mating actually are protected against parasites). This practice started to shift as knowledge about the risk of genetic defects from these relationships became better known. The U.S. then established laws prohibiting or regulating cousin marriages, and while they are still legal across Europe, they're generally frowned upon. However, consanguinity is a continued cultural practice to approximately ten percent of the world’s population. Only about one percent of that group is from the Western world, where negative social stigma toward consanguinity tends to be centralized. The difference in the prevalence of consanguinity across the world depends on local culture, geography, ethnicity, and religion.

Studies have found some social benefits to consanguineous relationships. These include a lower risk of financial problems, ease of marriage arrangements, increased female autonomy in heterosexual relationships, better compatibility with in-laws, preserved family wealth and values, shared cultural values, and lower rates of domestic violence and divorce. Some biological benefits from consanguineous mating are the likelihood of childbearing at an earlier age and thus a longer reproductive life, a higher number of live births, and an overall possible increase in fertility. However, most cons to marriage between cousins are focused on the genetic consequences of this pairing to any future children. First cousins have an up to three percent increased risk of having a child with birth defects or other potential disorders. These children are also at greater risk of having an autosomal recessive disease, which arises from an individual having both copies of a certain gene that isn’t working as it should. If blood relatives have children together, they’re more likely to carry the same recessive diseases and have a much higher chance of passing this on to their child. Possible conditions include (but are not limited to): immunodeficiency, diabetes, vision impairment, blood disorders such as sickle cell anemia, cancer, various heart diseases, asthma, intellectual disabilities, and infertility. Studies have also shown that children born from consanguineous relationships might have difficulty surviving until their own reproductive age, or greater difficulty finding a mate. If this child were to seek a nonconsanguineous partner, they then risk passing on their diseased alleles to the broader population.

For consanguineous couples who wish to have a child, they can limit the risk of passing on autosomal recessive disorders to their child by undergoing genetic testing under the care of a genetic counsellor. This process can be especially helpful if there is a family history of a particular disorder. A genetic counsellor can help diagnose your and your partner’s carrier status for autosomal recessive disorders. In the event that you and your partner would like to optimize reproductive outcomes with respect to potential genetic abnormalities, you might consider using in vitro fertilization (IVF) so you can select for embryos unaffected by genetic defects.

You mentioned that you and your cousin have a “don’t care” attitude towards others’ opinions about your romance, but it‘s great that you still made the effort to explore other perspectives and be better informed about your relationship. All that said, it sounds as though you and your partner have found something special in each other. No one knows where your dating relationship will lead—but it's good to be aware as you explore your closeness and make choices.

Last updated Dec 30, 2022
Originally published Oct 27, 1995

Submit a new comment


This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.

The answer you entered for the CAPTCHA was not correct.