The KJV phrase "sons of God" refers to the heavenly dimension state, i.e., the angelic body state.
Matt 22:30
30 For in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven.
KJV
1 John 3:2
2 Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is.
KJV
After Lord Jesus came and died on the cross, and The Father raised Him from the dead, all those in Christ now are called "sons of God", even women today. The reason why women in Christ Jesus are also now called "sons of God" too is because it refers to the angelic body state of the future, the "spiritual body" that Apostle Paul taught in 1 Corinthians 15. Per God's Word, the angels with that kind of body also, always appeared as men. Thus the "sons of God" reference for women in Christ also.
One gets that spiritual body type either at flesh death, or when one is changed on the day of Christ's future return. That spiritual body is what Paul also called "the image of the heavenly" that we shall be changed to, which points to what Jesus said above in Matthew 22:30 being MEANT LITERALLY ("but are as the angels of God in heaven", meaning in the same kind of heavenly body like the angels, which is a spiritual body, the image of the heavenly).
PRIOR to Christ's 1st coming, that phrase "sons of God" only referred to the angels in The Old Testament...
Job 1:6
6 Now there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them.
KJV
Thus it is very, very easy to understand that the "sons of God" in Genesis 6 was ALSO POINTING TO ANGELS that mated with flesh women to produce a hybrid giant race which God did not ordain.