The Sons
And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them, Genesis 6:1
Of Adam
which was the son of Adam, which was the son of God. Luke 3:38(c-d)
And The Daughters Of Eve
That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose. Genesis 6:2
This is a bit confusing to me.
Your post implies that the "sons of God" from Genesis are Adam. The verse you quote from Luke is the tail end of the complete recounting of Joseph's lineage, which goes from 3:23-38. Reading the entire passage, the implication with it ending in "Adam, which was the son of God" seems to be that it serves only to indicate which Adam is being referenced, essentially just drawing the recounting to a formal close. In any case, even if we take all instances of "son of God" in the Old Testament to refer to Adam, using the context of a verse from the New Testament, this presents a new choice of two problematic alternatives: Genesis 6:2 and 6:4 reference "sons of God"; if we are taking the phrase to mean "person directly created by God alone" and "son/daughter of man" to refer to "person created through human reproduction," then wouldn't there either have to be more than one man (and presumably, woman) created directly by God along with Adam (although not necessarily at the same time), or the appellation "son of God" in Luke bearing a meaning different from the one in Genesis?
Also, Genesis 6:4 talks about "giants in the earth" and relates them to the activities of "the sons of God" in a way that seems to indicate that the giants and the sons of God are not the same entities. It also states that the offspring of the sons of God and daughters of men "became mighty men which were of old, men of renown." What does this verse mean? The word choice is very peculiar.