Marriage between second cousins is legal in the United States and across the world. Cousin marriages are generally only restricted between first cousins.
Marriage between cousins is restricted or regulated in the United States to help prevent birth defects and genetic disorders in children. Birth defects are more common among children born to members of the same family. The rate of birth defects among children born to first cousins is 4 to 7 percent compared with 3 to 4 percent among the general population. The risk of birth defects rapidly diminishes the more distantly related two people are, and the risk is no longer significant among children born to parents who are second cousins.