Q: Hi Dan, sure but 1st I need to know who do u think the sons of God are ? The line of Seth or fallen angels ?
A: I have written on this subject many times (see Links below). I am going to assume you ask this question as a test, and to see if I may or may not agree with you, and I am assuming you are really asking about the "sons of God" in Genesis 6:4.
In the New Covenant writings the 'sons and daughters of God' are the believers and followers of YaHshua - 2 Cor 6:18 –
(2Co 6:18) and I will be a father to you, and you shall be sons and daughters to me, says the Lord Almighty."
The "sons of god" in Genesis 6:4 are not fallen angels as some very influential men in the Christian churches are teaching. To put it simply -- if these were fallen angels they would not be called "Sons of God", as fallen angels are "sons of Satan", not sons of God. Yes, in the first chapter of Job it appears the angels of YaHWeH are gathered around and called “sons of God”, but, if you take the time to read the account, you will see that among these righteous angels another appears among them and he is not called a son, but is called Satan – the Adversary. Satan is excluded from this title, as would be his angels, those fallen angels that joined him in the rebellion against their creator. In fact, in Rev 12 you will read that the fallen angels are called “his angels”, Satan’s angels. Keeping this in mind it should be an easy task to dispelling the false teaching that the “sons of God”, mentioned in Gen 6:4 is not demon angels.
As our Savior is the Son of God, and He calls us brothers -- Heb 2:11-12, and in reading 2 Cor 6:18, again, I guess you would have to say, We are the Sons of the Living God, if we call on Him, on our Savior, YaHshua -- Acts 4:12 & Rom 10:13.
This brings us right back to the Verse you mention, Gen 6:26 -- It is when Enoch is born that men began to call upon the Name of YaHWeH, and so, that would make them the infamous "sons of God", before they turned away from Him by marrying outside of their beliefs, becoming "unequally yoked" to unbelieving spouses, which, as in Solomon's later example, did not turn out so well. Saloon, a “son of God”, the king of all Israel, direct son of the flesh from King David, was led astray, even in all his wisdom by women he married outside of his faith, and he built prayer alters for them and even began to honor the false gods of his many wives. Solomon is a prime example of what happened to like-minded men in the pre-flood days and how they fell.
The following links will give greater detail and link to even more information on this subject.