Quote Originally Posted by Prince Laridus Konivaich
However, all humans are related, as shown by various reputable studies that trace all men back to a single ancestor, and all women back to a single ancestor. Since all humans are related, finding an unrelated mate would be impossilbe. This brings us back to the point that incest is an arbitrary line, which is reinforced by the fact that (as you mentioned) the definition of incest varies by state. Si first, I would suggest determining which definition of incest should be used by the law.
A pair of totally unrelated parents will have 23 pairs of genes each giving a total pool of 92 genes.

The total number of human genes is between 20,000 and 25,000. So you are playing in a shallow pool with a depth less then 1% of the true human gene pool if you are being incestous.