Elsewhere in the Bible, “Son of God,” is used to refer to angels, the nation of Israel, or to the Davidic king. But nowhere else does the Bible speak of someone being God’s “one and only Son.” Being the one and only (“begotten,” KJV) Son of God means that Jesus, unlike the rest of us, is not adopted into the family of God but is rather the eternal Son of God, the second person of the Trinity.
Kevin Vanhoozer