The reference of "sons of God" in Genesis 6:1-6, are not humans, keeper. Most people distinguish these passages of "sons of God" to be angels, not humans. The sons of God, known as the Watchers, or Griogriin Greek (should confused these Watchers in Buffy the Vampire Slayer) by the middle Second Temple Period (300-1 BCE), angels who had fallen, especially in the Book of Enoch, Book of Jubilee, Dead Sea Scrolls, and later in the Haggada.
Well, in the source I supplied, Genesis 6:1-6, was written in sort of historical way, which is usually taken literally. However, you say:
Are you indicating the angels (sons of God) are not begotten by God, literally?
If you do, then I find this to be very strange. Strange, because you would take something that are written literally (Genesis 6:1-6) to be taken metaphorically (like the "sons of God"). But with both Revelation and John 1 (with regards to the "Word"), which I would view as allegory or parable, but for you (and other Christians like you), would take it all literally what was written only in metaphorical manner.
It's probably why I don't understand Christians. You pick and choose which parts of the bible to take literally, and others part you would see as metaphors, parables or allegory.