There is a case right now of a father and a daughter who were separated when she was young. They met, formed a sexual relationship, then found out they were related.<quoted text>Incest is not natural. Homosexual behavior is prevalent in nature, but incest is not. Incest is prevalent in the bible though. In fact, the claim of the bible shows all humans are the product of two relationships of incest, Adam and Eve, and Noah and his family.
Incest is known to result in deformations in offspring. This alone will keep it off the list of what our government will condone.
They are trying to prove that there is a biological attraction there because they are blood related, when in most cases, if they had been able to stay together, forms a mental block that tells the brain that person is off limits. Kinda like if your sister was hot, you'd still think she was gross. But if you were separated, you wouldn't see it that way. In other words, they are trying to prove that this is natural, and biologically sound.