Jesus was not born of blood, nor of the will of the flesh, nor of the will of man.
Jesus was born of God, called the only Begotten of God, called the Son of God.
John 1:13 is not saying the Son was not born of the flesh and blood of men and women like other babes. The Son, like all born again sons, was made and born of flesh and blood of men and women.
Concerning his Son Jesus Christ our Lord, which was made of the seed of David according to the flesh; And declared to be the Son of God with power, according to the spirit of holiness, by the resurrection from the dead:
For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son?
The baby Jesus was conceived and nurtured from the flesh and life's blood of Mary (Who also had the seed of David by her parents), And was declared to be the son of God come in the flesh of man and woman on earth.
He was the Word made flesh of man and woman, and the Son declared to be born of blood of man and woman.
And the angel answered and said unto her, The Holy Ghost shall come upon thee, and the power of the Highest shall overshadow thee: therefore also that holy thing which shall be born of thee shall be declared the Son of God.
Jesus' body was conceived by the Spirit from the flesh and blood of Mary's womb, wherein was the seed of David's loins.
Therefore being a prophet, and knowing that God had sworn with an oath to him, that of the fruit of his loins, according to the flesh, he would raise up Christ to sit on his throne;
I really don't know how many times and ways God can say something so simple and plain.
But then, if one plain verse doesn't convince the unbeliever, there is no amount of verses that will do it.
I believe that's why God writes His words, so that we must read them with honest faith. And even if he did write a verse saying, "Jesus Christ My only begotten Son came in the same exact flesh of all men and women!" An unbeliever still wouldn't believe it.
Oh wait, He did say that didn't He? Just not in the same exact verse.
And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that spirit of antichrist, whereof ye have heard that it should come; and even now already is it in the world.
Wherefore in all things it behoved him to be made like unto his brethren, that he might be a merciful and faithful high priest in things pertaining to God, to make reconciliation for the sins of the people.