The angels that chose to go with Lucifer left their first estate, as I figure it.
Anyway I think I can show you it was Adam that was the son of God.
Luk 3:38 Which was the son of Enos, which was the son of Seth, which was the son of Adam, which was the son of God.
If Adam was the son of God, then Adam's boys would be grandsons of God, right?
Now we look at this scripture:
Job 1:6 Now there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them.
Job 2:1 Again there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them to present himself before the LORD.
Son's of God, Adam and his sons, came to present themselves and Satan just came along.
Now this is what I want to point out
Gen 6:1 And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them,
Gen 6:2 That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose.
The 'sons of God' saw the 'daughters of men'
Sons of God saw the daughters of men, not daughters of God. Do you see it?
The sons of God would have seen their sisters every day, it is saying they saw these daughters of men and were fair and they took them wives.
Sons of God, Adam and his sons.
Daughters of men, those would be daughters of mankind created in Gen 1.
Two creations, Gen 1(mankind) and Gen 2(Adam, son of God)