Now it came about, when Abram entered Egypt, that the Egyptians saw that the woman was very beautiful. Pharaoh’s officials saw her and praised her to Pharaoh; and the woman was taken into Pharaoh’s house.
Genesis 12:14-15 (NASB)Now it came about, when mankind began to multiply on the face of the land, and daughters were born to them, that the sons of God saw that the daughters of mankind were beautiful; and they took wives for themselves, whomever they chose.
Genesis 6:1-2 (NASB)
The scriptures echo. Or perhaps a better way of describing it is that the later instances are parables to teach you the meaning of the earlier ones.