Cousin marriage is a bad analogy.
First cousins may legally marry with no restrictions in the following states: Alabama, Alaska, California, Colorado, Connecticut, Florida, Georgia, Hawaii, Maryland, Massachusetts, New Jersey, New Mexico, New York, North Carolina, Rhode Island, South Carolina, Tennessee, Vermont, and Virginia.
Arizona, Illinois, Indiana, Maine, Utah, and Wisconsin allow first cousins to marry under certain circumstances.
The rest of the states have prohibited it. However, as far as I know, none of them refuse to recognize as valid cousin marriages that were performed in the states where it is legal.
No it’s not. It’s a valid law in most states and widely-assumed premise everywhere. The point is close-family relations is anathema as is polygamy and under-age. There are laws on the books. Meanwhile I’m unaware of ANY old laws that specifically prohibit male-male/female-female marriage - that was just assumed!