Genesis 6 · a question people ask
Who were "God's sons" and the Nephilim?
Verses 1-4 are among the hardest in Genesis, and Protestants read them in three main ways. Verse 4 doesn't say whether the Nephilim were the children of these marriages; it says they "were on the earth in those days, and also after that". All agree the passage shows evil spreading, which leads straight into the flood.
How Christians read it
Where Christians differ, Favor sets out the main views side by side and doesn't pick one.
Angels
"God's sons" means heavenly beings, as it does in Job ("God’s sons came to present themselves before the LORD", 1:6; "all the sons of God shouted for joy", 38:7). Some connect this with the angels in Jude 6 and 2 Peter 2:4 who sinned and are kept for judgment.
Job 1:6 · Job 38:7 · Jude 1:6 · 2 Peter 2:4
Seth's line and Cain's line
"God's sons" are the descendants of Seth, who called on the LORD (4:26), and "men's daughters" are from Cain's line. The sin is the faithful family marrying into the ungodly one and losing its way. Those who hold this view also point to Matthew 22:30, where Jesus says that in the resurrection people don't marry but "are like God’s angels in heaven", and take it to mean angels don't marry.
Genesis 4:26 · Genesis 5:1-32 · Matthew 22:30
Powerful rulers
"God's sons" are kings or rulers who claimed divine status and "took any that they wanted" as wives. Those who hold this view point to verse 4's "mighty men… men of renown", and to Psalm 82:6 ("You are gods, all of you are sons of the Most High"), which they read as spoken to human rulers.
Genesis 6:2 · Genesis 6:4 · Psalm 82:6