I believe that "Sons of God" in the OT are angels in every case.
In Jude, this passage speaks of those angels who "left their own habitation" and did as those in Sodom and Gomorrha and committed fornication and went after strange flesh. This is why they are reserved in everlasting chains until the judgement of the great day. They can't be asexual if they are "giving themselves over to fornication".
Jude:
6 And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.
7 Even as Sodom and Gomorrha, and the cities about them in like* manner, giving themselves over to fornication, and going after strange flesh, are set forth for an example, suffering the vengeance of eternal fire.
These are the angels, sons of God, in Genesis 6.