Your the first person I have ever heard to to argue that Jesus did not exist until he was born.
except those who deny the trinity.. Not sure what your trying to prove here.
Before Jesus was conceived by Mary, He was not the Son of God.
God is the divine family. He was one of that family.
In John 1:1 He is called the “Logos”—the Word. He, like the Father, had existed eternally.
But He is nowhere in God’s Word referred to as a son of God prior to conception by Mary.
His human birth was His first birth[seed of David]. He gave up the glory He had with the
Father in order to be born into the world to save the world.
The Word was [with] God
at that prehistoric time of the first verse of John 1, the Word was not (yet) the Son of God.
He divested himself of His glory as a spirit divinity to be begotten as a human person.
He was made God’s Son, through being begotten or sired by God and born of the virgin Mary,
and later [resurrected] as the firstborn Son of God, declared Son of God at his second birth.
“And declared to be the Son of God with power, according to the spirit of holiness,
by the resurrection from the dead.”