In the beginning, God created all things. But some fallen angels trying to be a cheap imitation of God creating things, created the half human, half fallen angel that we called the "giants" that were killed in the flood, except the few that were aquatic and I dont doubt those were destroyed in other ways and then those dead giants became evil spirits roaming the land angry at God and man. God did not create the giants. But even the fallen angels didnt do what God did, he created everything out of nothing and they only modified the life He had already created.
Nothing was created by any angel nor by fallen angel except by the Word of God.
John 1:1In the beginning was the Word, and the Word was with God, and the Word was God. 2 The same was in the beginning with God.
3 All things were made by him; and without him was not any thing made that was made. 4 In him was life; and the life was the light of men.
All births from the womb is from the Lord.
Psalm 12:3 Lo, children are an heritage of the Lord: and the fruit of the womb is his reward.
Angels were not created to have families; So even in a fallen state, they still cannot reproduce.
Mark 12:24 And Jesus answering said unto them, Do ye not therefore err, because ye know not the scriptures, neither the power of God? 25 For when they shall rise from the dead,
they neither marry, nor are given in marriage; but are as the angels which are in heaven.
The sons of God cannot be angels nor would they still be called as sons of God as being fallen angels. The sons of God can only refer to Israel's family tree; their roots; stemming from Seth's bloodline as replacing what should have been Abel's godly lineage.
God would not join an angel nor a fallen angel in "holy matrimony" for that woman to be called a wife in His word to that "angel" or "fallen angel".
Only the Lord can help you see the Book of Enoch for the fraud that it is in order to disregard it because it is running against the truths in His words in the accepted scripture of the 66 Books of Bible.