I've studied the verses where that occurs.
The expression 'Sons of God', is like this in the manuscripts:
'giants that were downfallen angels'
The expression 'Sons of God' occures a few times in the Bible, for example in the book of Job, & always means that.
Genesis talks about giants taking doughters of humans. That was Satans plan to spoil the humankind so that Jesus could not be born from a human woman. But the plan sure failed. God threw all those giants to hell ages ago, that is also mentioned in the Bible.