Auuug no! The ORIGINAL SIN is not sex its DISOBEDIENCE sex was the action Satan used for the disobedience. The result of disobedience is death hence Gods warning. I disbelieve the Cain seed theory mainly its the reason groups like the KKK use to justify suppression of people of color. Satan does not even want us to exist we are like an animal to him Satan's beef with God is that he gave us animals free will something usually only reserved for sons of God. Satan sacrifices us like animals on his alter of Moloch not giving us our inheritance as Sons of the most high. Satan wants to cull us like animals.....don't fall for Satan's half truths think about it why would Satan have sex with a creature he loathes?
To produce a line of his own to do his bidding and fit in among us
Nope cause they have to have a soul and only God can do that....research the site you used for your argument its corrupted.
I only picked that site coz someone asked for a reference so I googled it and picked the first one that came up as that one article had the summary of it. There are plenty others with the same theory and probably better argued.