The writers of the gospels had different agendas, so the gospels often conflict with each other in the details even though they stick to the same storyline because of their literary interdependencies. It's amusing how historians can discern those agendas just by comparing the texts. That's likely one reason why the Western Church hid the texts by not translating them into a common language.

The Virgin Birth story is a classic example of how the gospel authors were tailoring their story to the literary conventions of heroism. Greco-Roman heroes often had virgin births because they were demigods.