Not quite.
The BOOK does NOT make that claim.
4 The Nephilim were on the earth in those days—and also afterward—when the sons of God went to the daughters of humans and had children by them. They were the heroes of old, men of renown.
5 The Lord saw how great the wickedness of the human race had become on the earth, and that every inclination of the thoughts of the human heart was only evil all the time. 6 The Lord regretted that he had made human beings on the earth, and his heart was deeply troubled. 7 So the Lord said, “I will wipe from the face of the earth the human race I have created—and with them the animals, the birds and the creatures that move along the ground—for I regret that I have made them.” 8 But Noah found favor in the eyes of the Lord.
It does NOT say the GIANTs mated with the Humans; it merely says they were on the earth. So; just WHO are the sons of God and the daughters of humans??? The BOOK says: Let Us create Man in Our image. So there you get some 'sons of God'; right?? The BOOK also says, in Genesis 5:3-4 When Adam had lived 130 years, he had a son in his own likeness, in his own image; and he named him Seth. 4 After Seth was born, Adam lived 800 years and had other sons and daughters. These things happened BEFORE Genesis chapter 6....