Its completely legal, but definitely not as common as it once was. It was once common practice, but marrying your cousin has fallen out of fashion in recent times – thankfully, some would say.
Is it OK to have a relationship with your second cousin?
In the United States, second cousins are legally allowed to marry in every state. However, marriage between first cousins is legal in only about half of the American states. All in all, marrying your cousin or half-sibling will largely depend on the laws where you live and personal and/or cultural beliefs.
Are eighth (8th) cousins blood related? We are unlikely to share DNA with our 8th cousins. Eighth cousins have only about a . 24% chance of showing up as DNA matches to each other.
Why is it not good to marry your cousin?
Children of first-cousin marriages have an increased risk of autosomal recessive genetic disorders, and this risk is higher in populations that are already highly ethnically similar. Children of more distantly related cousins have less risk of these disorders, though still higher than the average population.