Could the stories of Greek gods originate in the Nephilim of Genesis 6?
In Genesis 6, the Bible seems to suggest that the mythology of ancient cultures, including Greek and Roman mythology, may have found its source in the historical accounts of misbehaving demons. In the days prior to the flood, demons (fallen angels) committed gross sin by mating with earthly women to produce an unnatural, powerful offspring called Nephilim:
Gen. 6:1 Now it came about, when men began to multiply on the face of the land, and daughters were born to them,
Gen. 6:2 that the sons of God saw that the daughters of men were beautiful; and they took wives for themselves, whomever they chose.
Gen. 6:3 Then the Lord said, “My Spirit shall not strive with man forever, because he also is flesh; nevertheless his days shall be one hundred and twenty years.”
Gen. 6:4 The Nephilim were on the earth in those days, and also afterward, when the sons of God came in to the daughters of men, and they bore children to them. Those were the mighty men who were of old, men of renown.
The offspring of the demons (i.e., the "sons of God") and earthly women were Nephilim. They were mighty men of ancient times and were renown, meaning their strength and accomplishments were legendary. Nevertheless, these “creatures” polluted the line of humanity, threatening God's plan to produce a Messiah in the seed of men, so God brought the flood to the earth to destroy all flesh including the Nephilim. Meanwhile, the legends of this strange and powerful human-like creatures lived on in the mythology of ancient man.
For more background, please read our article on Nephilim. You may also find our Genesis Bible study helpful.
