Sometimes coincidences happen and sometimes human stories independently converge on specific tropes.
Like how evolution keeps making more and more things into crabs, or how flight developed indepently in multiple different branches of the tree of life, same with eyes, I think.
Also, Jesus virgin birth isn't even fully agreed upon by early Christians.
The word that is translated as 'virgin' in most modern Bibles ... actually just means 'young woman.'
Sure, its doctrine now, but it wasn't originally.
EDIT:
A number of Christian detractors in the early days actually spread a story that Mary had been impregnated by a specific Roman soldier, and that Joseph, a much older man, possibly a widow... basically pity married her, because ... well, being an unmarried 15 yo pregnant with the son of a hated, occupying, heathen military force?
She'd be lucky to not be stoned to death.
Frankly, its a historically plausible story, but there's no real way to evaluate whether or not it is actually true.