This Bible contradiction is from the Skeptic's Annotated Bible.

Verses

God has only one son (Jesus).

John 3:18 View context

He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.

1 John 4:9 View context

In this was manifested the love of God toward us, because that God sent his only begotten Son into the world, that we might live through him.

Adam was also God's son.

Luke 3:38 View context

Which was [the son] of Enos, which was [the son] of Seth, which was [the son] of Adam, which was [the son] of God.

Some of God's sons had sex with women producing a race of giants.

Genesis 6:2-4 View context

That the sons of God saw the daughters of men that they [were] fair; and they took them wives of all which they chose.

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.

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.

Satan and his companions were sons of God.

Job 1:6 View context

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 View context

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.

God's sons were present when the universe was created.

Job 38:6-7 View context

Whereupon are the foundations thereof fastened? or who laid the corner stone thereof;

When the morning stars sang together, and all the sons of God shouted for joy?

Christians are God's sons.

John 1:12 View context

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: