Taking into account the ambiguity of Genesis 6:4, how can we know the origin of Nephilim?

**Some preliminary notes:** 1. No, this is not a hermeneutical question, as what I’m interested in are answers from theological perspectives who advance/defend the notion which states that the Nephilim mentioned in Genesis 6:4 are in fact the offspring of the sons of God mentioned in the same verse. 2. Separate is the question of the identity of the aforementioned “sons of God.” Instead, my inquiry is strictly about how the ancestry and origin of the Nephilim have been deduced from scripture according to any and every denomination who espouses such knowledge. **The verse** Here is the verse in question, from various English translations: > The Nephilim were on the earth in those days, and also afterward, when > the sons of God came in to the daughters of man and they bore children > to them. These were the mighty men who were of old, the men of renown. > **ESV** > The Nephilim were on the earth in those days—and also afterward—when > the sons of God went to the daughters of humans and had children by > them. They were the heroes of old, men of renown. **NIV** > The Nephilim were on the earth in those days (and also after this) > when the sons of God were having sexual relations with the daughters > of humankind, who gave birth to their children. They were the mighty > heroes of old, the famous men. **NET** > There were giants in the earth in those days; and also after that, > when the sons of God came in unto the daughters of men, and they bare > children to them, the same became mighty men which were of old, men of > renown. **KJV** **The question** It seems clear to me from a plain, common sense reading of the verse that the Nephilim preexist the event in which the sons of God have offspring with the daughters of men. How can anyone claim that they originate from said relations? Simple question, hoping for a simple answer. God bless!