Think they're not related?
Think again.
Dust off those old history books, or surf over to Wikopedia [ignore my spelling]

OK!

Between 14 BC and upto around 6-8 BC, the Roman Emperor, Augustus Caesar carried out a long, EXPENSIVE campaign to conquer the mineral
rich Iberian [Spanish] territories...
The long campaign nearly exhausted the Roman treasury.

What was poor Caesar to do to replenish the Roman treasury?

Did somebody say "tax" the Roman world?
That's exactly what he did.

But!...He needed to carry out an empire-wide census and registry first; to know how many he could tax, who were taxable, and where they would pay their taxes.

That's where Mary and Joseph enter the picture.
They received the Roman proclamation in Nazareth.
Nazareth was not Joseph's hometown; as the descendent of King David,
he needed to go to his hometown [Bethlehem] to register and to take part in both the census, first, and [a year or two later] to pay the tax required
of him.

So?
So Jesus would NOT have been born in Bethlehem, and would NOT have fulfilled a prophecy/prediction made by a Jewish prophet, Micah, made hundreds of years before ["And you Bethlehem of Judea, are by no means least among the leaders of Judah, For out of you shall come forth a Ruler..."] were it not for the fact that Augustus Caesar had to fight a war and costly campaign in Iberia.

Amazing how historical events tied together so harmoniously,