This story about fallen angles mating with earthly woman, came from a commentary written by a man based on his own thoughts about what the Bible said. It has never been based on scripture. This story has spread like wild fire through the churches because it is easier for man to just take the preachers word over studying to prove what is true. Satan knows how lazy man is and that man will not study for himself to know what is true. He keeps doing the same thing he did since the day he deceived Eve. Eve just took his word for it rather than go to God and see what he had to say about it. It is easier to just except a lie rather than admit God has all the answers.
Acts 17:11 (KJV)
11 These were more noble than those in Thessalonica, in that they received the word with all readiness of mind, and searched the scriptures daily, whether those things were so.
1 Thessalonians 5:21 (KJV)
21 Prove all things; hold fast that which is good.
2 Thessalonians 2:10-12 (KJV)
10 And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
11 And for this cause God shall send them strong delusion, that they should believe a lie:
12 That they all might be damned who believed not the truth, but had pleasure in unrighteousness.
The passage about the sons of God take wives of men has been taken out of context. You must read what the passage says not what you think it says.
Genesis 6:1-4 (KJV)
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.
Look at verse 4. We are told there were already giants in the earth at the time the sons of God took of the daughters of men, and there were still giants in the earth after that. Then it goes on to tell us the these children became mighty men, well know, (famous if you will). It does not say they became giants. The giants were already there.
Lets take a look a a few passages and see who God tells us the sons of God are.
Hosea 1:10 (KJV)
10 Yet the number of the children of Israel shall be as the sand of the sea, which cannot be measured nor numbered; and it shall come to pass, that in the place where it was said unto them, Ye are not my people, there it shall be said unto them, Ye are the sons of the living God.
1 John 3:1-2 (KJV)
1 Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not.
2 Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is.
Philippians 2:14-15 (KJV)
14 Do all things without murmurings and disputings:
15 That ye may be blameless and harmless, the sons of God, without rebuke, in the midst of a crooked and perverse nation, among whom ye shine as lights in the world;
John 1:11-12 (KJV)
11 He came unto his own, and his own received him not.
12 But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name:
Romans 8:14 (KJV)
14 For as many as are led by the Spirit of God, they are the sons of God.
Also lets look at the beginning of the lineage of from Adam to Jesus.
We see Adam was the son of God, so if Adam was the son of God, do you not think much of his seed whould have also been called the sons of God?
Luke 3:38 (KJV)
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.
Now lets take a look at what God says about the angles being called sons of God.
Hebrews 1:5 (KJV)
5 For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son?
God never once called the angles sons of God. But he did call faithful man sons of God!
Ok so who are the daughters of men?
we see in many passages that sons of men is refering to the ungodly (unbelieving), this would also include the daughters.
Lets look at a few passages to get a better understanding of this.
Ephesians 3:4-5 (KJV)
4 Whereby, when ye read, ye may understand my knowledge in the mystery of Christ)
5 Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit;
Ecclesiastes 8:11 (KJV)
11 Because sentence against an evil work is not executed speedily, therefore the heart of the sons of men is fully set in them to do evil.
Ecclesiastes 9:3 (KJV)
3 This is an evil among all things that are done under the sun, that there is one event unto all: yea, also the heart of the sons of men is full of evil, and madness is in their heart while they live, and after that they go to the dead.
Psalm 4:2-3 (KJV)
2 O ye sons of men, how long will ye turn my glory into shame? how long will ye love vanity, and seek after leasing? Selah.
3 But know that the LORD hath set apart him that is godly for himself: the LORD will hear when I call unto him.
This is a very breaf overview to this study. If I were to cover every bit of this study and all the scripture that goes with it, the exausted study of this subject takes about 6 hours to cover.