Incest... Not... Opps... Strike That

[Ms. Toad]

7. Aside from isolated cases like this with a known hereditary disease, where genetic counseling is appropriate,

Or situations in which the entire gene pool is very, very limited (not just the couple, but an isolated community with lots of intermarrying), the most recent research indicates that there is very little difference in genetic health between marriage of unrelated individuals and between first cousins.

The most recent studies suggest that random couples have a 2-4% chance of an inherited disease, whereas first cousins have a 3.7-6.8% chance. NYTimes

There are diseases where there is a lot of risk, far more than that which comes from a marriage among cousins, and there is no prohibition on (for example) people with Tay Sachs, Huntington's Disease, Marfan syndrome, Achondroplasia marrying. Two African American individuals have a higher risk of sickle cell anemia than average, and there isn't a suggestion they should be prohibited from marrying.

Not to mention that not every marriage results in children.