This is the story as it has been given to us.
The Birth of Jesus - According to Matthew (1: 18 – 25)
Now this is how the birth of Jesus Christ came about. When his mother Mary was betrothed to Joseph, but before they lived together, she was found with child through the Holy Spirit. Joseph her husband, since he was a righteous man, yet unwilling to expose her to shame, decided to divorce her quietly. Such was his intention when, behold, the angel of the Lord appeared to him in a dream and said, “Joseph, son of David, do not be afraid to take Mary your wife into your home. For it is through the Holy Spirit that this child has been conceived in her. She will bear a son and you are to name him Jesus, because he will save his people from their sins.” All this took place to fulfill what the Lord had said through the prophet: “Behold, the virgin shall be with child and bear a son, and they shall name him Emmanuel,” which means “God is with us.” When Joseph awoke, he did as the angel of the Lord had commanded him and took his wife into his home. He had no relations with her until she bore a son, and he named him Jesus.
The Birth of Pythagoras - According to Iamblichus
Mnesarchus and Pythais, the parents of Pythagoras, descended from the family of Ancaeus, he who was ordered by the Pythian oracle to colonize the Island of Sarnos, taking people from Arcadia and Thessaly as well as from Athens, Epidourus and Chalcis. Pythagoras was also called the Son of Apollo, which seems to have originated from a prediction made by the Pythian oracle to Mnesarchus that he would have a son surpassing in beauty and wisdom all that had ever lived and who would be of the greatest advantage to the human race, in everything pertaining to the life of man. When the child was born at Sidon, in Phoenicia, he was named Pythagoras, signifying that such an offspring had been predicted by the Pythian Apollo.
As in Matthew and Luke, statements about Pythagoras’s ancestry are combined with affirmations of a supernatural birth.
1) In the Gospels neither the genealogy nor the miraculous birth are the basis of Jesus’ abilities and deeds. Iamblichus, however, gives the genealogy to account for the hero’s amazing ability.
2) For Pythagoras, the progenitor of the family line was himself begotten by Zeus. According to the Nicene Creed, adopted at the First Council of Nicaea in 325, Jesus himself was begotten by God,
“Born of the Father before all ages; God from God, Light from Light, true God from true God, begotten, not made, consubstantial with the Father; through him all things were made.” (Catholic Church’s Creed)
3) The “dualism” of Iamblichus ( a human body born in the natural manner but a divine soul that came from heaven) is also in contrast to the Gospels’ lack of interest in the nature of Jesus, as is Iamblichus’ attempt to combine a kind of “preexistence” with a human birth.
“According to the ancient theology, between those perpetual attendants of a divine nature called essential heroes, who are impassive and pure, and the bulks of human souls who descend to earth with passivity and impurity, it is necessary that it should be an order of human souls who descend with impassivity and purity, for as there is no vacuum, either in incorporeal or corporeal natures, it is necessary that the last link of a superior order, should coalesce with the summit of one proximately inferior. These souls were called by the ancients, terrestrial heroes, on account of their high degree of proximity and alliance to such as are essentially heroes. Souls of this kind descend into mortality both to benefit other souls and in compliance with that necessity by which all natures inferior to the perpetual attendants of the gods are obliged to descend. Hercules, Plato, Theseus, and Pythagoras were of this order of souls.”