Expressly the angels of God IN HEAVEN, do not marry.
Angels on Earth did take human wives, have offspring.
Angels on Earth who did take human wives....remained on Earth, as their “estate”. Ie they did not return to Heaven.
Are angels able to change themselves to reproduce once fallen from their first estate from Heaven? No. Only God can do that & He didn't.
If they were originally created to not marry nor given in marriage, then why would God do that for fallen angels?
Is not God the One that joins a man and a woman together as one flesh for that woman to be named a "wife" to that man?
Why would God, Who knows all things, help fallen angels to join with women in "holy matrimony" if their diabolical plot was to pollute the bloodlines of mankind to prevent the coming of the Christ child?
Once you recognize that God would never joined the "sons of God" with women unless they were of Israel's family blood line of Seth, to build families but doing so as outside of the godly lineage of Seth ( Like Isreal is not to marry outside the nation of Israel ), you will see that "fallen angels" would never be identified as the "sons of God" in scripture, let alone the women they marry be called "wives" to them for God would not join them together.
John 3:6
That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
It is that first part I am referring to for why celestial beings cannot reproduce. Now note what happens after the reproduce.
Genesis 6:1 And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them,
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. 3 And the Lord said, My spirit shall not always strive with man,
for that he also is flesh: yet his days shall be an hundred and twenty years.
4 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.
Still men. Not spirits or watchers like that fake Book of Enoch says.
Now note the real reason God flooded the world. It wasn't for the fallen angels trying to pollute the bloodlines but for another reason of man.
5 And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually. 6 And it repented the Lord that he had made man on the earth, and it grieved him at his heart. 7 And the Lord said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them. 8 But Noah found grace in the eyes of the Lord.
God reaffirms afterwards that is the main and only reason He sent the global flood.
Genesis 8:20 And Noah builded an altar unto the Lord; and took of every clean beast, and of every clean fowl, and offered burnt offerings on the altar. 21 And the Lord smelled a sweet savour; and
the Lord said in his heart, I will not again curse the ground any more for man's sake; for the imagination of man's heart is evil from his youth; neither will I again smite any more every thing living, as I have done. 22 While the earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease.
Ask the Lord for wisdom to see the truth in His words rather than trying to fit that fake Book of Enoch into His words.