Lord's Day 13

33. Q. Why is He called God's "only Son" when we are God's children?
A. Because Christ alone is the eternal, natural Son of God. We, however, are adopted children of God - adopted by grace through Christ.

34. Q. Why do you call Him "Our Lord"?
A. Because - not with gold or silver, but with HIs precious blood - He has set us free from sin and the tyranny of the devil and has bought us, body and soul, to be His very own.

"The Sonship of Jesus Christ, then, is different from ours in that we became children of God, whereas Jesus Christ has always been God's Son. Jesus was not made the Son of God at His Incarnation as if some new title or identity was conferred upon Him. The Son of God was the Son of the Father even before creation (Heb. 1:2). His Sonship is eternal. Ours is not. That's the difference. By nature, we are not God's children, whereas Christ is by nature the Son of God.

"But with all this talk of Jesus as the Son of God, we must not presume that God is a Father to the Son as a man is a father to his son. . . [T]he Son of God never came into being. He is God's eternally begotten Son. There never was a time when He was not. The Father did not give life to Him in the sense that He created the Son or brought the Son from nonbeing to being.

"Rather, the Father shares His essence with the Son and the life He has in Himself (John 5:26). So for us, being called children of God means we have been given new life and graciously welcomed into the family of our heavenly Father. But for Jesus to be called God's only Son means that He shares equally in divinity, glory, and honor with the Father. Sometimes liberal theologians have argued that Jesus believed He was the Son of God in the same way that we are God's children, but this was plainly not the case. Even the Jews understood that when Jesus declared His radical  unity with the Father as His only Son, He was daring to make Himself not just a spiritual child of God but equal to God Himself (John 5:19).

The Good News We Almost Forgot, Kevin DeYoung, Moody Publishers, 2010, pg. 70-72.