If you mean merely living physical existence I understand the conception to death definition of "existence" but it is worth noting that there's quite a few references indicating that Jesus actually existed (creation of the earth, casting down the devil, speaking to Moses, mourning over the prophets that Jerusalem killed) before he physically existed.
Matthew 23:37 KJV
(37) O Jerusalem, Jerusalem, thou that killest the prophets, and stonest them which are sent unto thee, how often would I have gathered thy children together, even as a hen gathereth her chickens under her wings, and ye would not!
Revelation 12:9 + Isaiah 14:12 + Luke 10:17-18 KJV
(9) And the great dragon was cast out, that old serpent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.
(12) How art thou fallen from heaven, O Lucifer, son of the morning! how art thou cut down to the ground, which didst weaken the nations!
(17) And the seventy returned again with joy, saying, Lord, even the devils are subject unto us through thy name.
(18) And he said unto them, I beheld Satan as lightning fall from heaven.
John 1:1, 3, 14 KJV
(1) In the beginning was the Word, and the Word was with God, and the Word was God.
(3) All things were made by him; and without him was not any thing made that was made.
(14) And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
John 8:57-58 KJV
(57) Then said the Jews unto him, Thou art not yet fifty years old, and hast thou seen Abraham?
(58) Jesus said unto them, Verily, verily, I say unto you, Before Abraham was, I am.
John 17:5 KJV
(5) And now, O Father, glorify thou me with thine own self with the glory which I had with thee before the world was.
Colossians 1:15-16 KJV
(15) Who is the image of the invisible God, the firstborn of every creature:
(16) For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by him, and for him:
Isaiah 48:12-13 + Revelation 1:17-18 KJV
(12) Hearken unto me, O Jacob and Israel, my called; I am he; I am the first, I also am the last.
(13) Mine hand also hath laid the foundation of the earth, and my right hand hath spanned the heavens: when I call unto them, they stand up together.
(17) And when I saw him, I fell at his feet as dead. And he laid his right hand upon me, saying unto me, Fear not; I am the first and the last:
(18) I am he that liveth, and was dead; and, behold, I am alive for evermore, Amen; and have the keys of hell and of death.
When the volume of references reach that level and amount, it becomes less plausible that these are all misunderstood coincidence. So far (above) I've got a running count of seven. Maybe more or maybe less depending on how they are grouped or tallied (by styles of reference or by passages?)