Genesis 6:1-8 has several interpretations. The differences in these views center on the identification of those referred two as “the sons of God” and the other details of each view extends from who “the sons of God” are identified as. There are three main views on this: Sethites, Rulers, and Fallen angels.
Another view is that the sons of God were pre Flood believers. This view has scriptural support and also explains more than it was designed to support.