The Sons of GOD include every person ever created in HIS image ie, able to become a proper Bride for HIM. They all had a free will and an equal ability and opportunity to put their faith in HIM as their GOD and saviour OR to rebuke HIM as a liar and therefore a false god.
The image of God is not man. The image of God is the Son. There is no better image of a Holy Father than a Holy Son. We are being conformed into the image of Christ and not Adam for very good reason. There's nothing redeemable in man. But there is everything worthwhile in God's Son.
There is no free will. Free will is an illusion. God knows the beginning from the end because He ordained the end. God could not do this if man truly had free will.
God's will is Sovereign.
There is "no opportunity to put faith in Christ" for men are dead in trespasses and sin and Scripture says everything about salvation is a gift of God even faith.
Once someone chose to rebuke HIM, sinning the unforgivabe sin,
The unforgivable sin cannot be committed by born again believers because they are in the hands of the Father and the Son and no one can pluck them out of that security, not even the person.
The unforgivable sin is being unatoned and non-elect of God.
they became reprobate illegitimate children by this choice:
Deuteronomy 32:5 “They have corrupted themselves; They are not His children because of their blemish but a perverse and crooked generation.
OR
their blemish is that they are not HIS children.
The Abrahamic Covenant insured Abraham and his descendants many promises both natural and spiritual.
The covenant was with Abraham and his descendants and God cannot lie. He will keep all His promises even though frail sons do not. What happen to Israel in the First Covenant is happening to the Gentile Church today. Disobedience, rebellion, false gods, you name it they have done it. But if they are saved, they are still God's adopted children and God will keep His promises to Abraham/children of Israel.
But merely choosing to become sinful is not the criteria for losing the status of being HIS children because sinful legitimate children are mentioned in Heb 12:8. The sin that would seem to be much worse than the sin of the elect legitimate children to be so totally corrupting of themselves so it must be the unforgivable sin of totally repudiating HIM by their free will thereby joining the ranks of the people of the evil one sown into the earth by the devil, Matt 13:36-39.
One can tell the difference between wheat and tares.
Free will in man and angel is an illusion. There is only God's will.
Since ALL the sons of GOD saw HIS creation of the physical universe, these sons must have been in spirit form as pre-physical but they were not angels because angel is a job description, not a race or type of being / person.
What's the possibility in your mind an "angel" of God is actually His Word spoken?