(I usually repost this article during Advent because the question keeps coming up.)
Everyone is familiar with the fact that Jesus' parents couldn't find a place to stay when they arrived in Bethlehem. But why didn't just stay with relatives? After all, this was supposedly Joseph's hometown.
Luke, who tells this story in the 2nd chapter of his Gospel, does not elaborate. To him the point is that the King of the Universe was born in the most abject of circumstances -- abject to the point that he had to be laid in a feeding trough.
Even if there had been "room for them in the inn," the surroundings would not have been opulent. The "inn" of a small, first century, middle eastern village like Bethlehem would have been a few crude lean-to's for traveling people and animals found on the edge of town. Even those were full, and very old tradition says Mary and Joseph found shelter in a little cave (more like a nook in the rock).
But what about Joseph's relatives? Scholars put forward two possible reasons they didn't provide shelter for the two travelers that night (aside from suggesting Mary and Joseph never went to Bethlehem, which we will deal with elsewhere). Both are conjectures of course and neither is supported by any of the early Christian writers, so you can decide for yourself which seems more likely.
One explanation is that Joseph may not have had any relatives in Bethlehem. He and Mary traveled there because it was the ancestral home of King David, Joseph's ancestor, but it's quite possible that in the 1000 years since David's time his descendants had spread to the four winds. Joseph had, of course. At some point he or his family had chosen to move 90 miles north to tiny Nazareth.
This possibility is made more likely by the fact that, being of royal stock, the family of David was often a target of suspicion by the authorities. We know for instance that relatives of Jesus were examined at the end of the first century for just this reason. So the harder it was for current rulers like Herod and the Romans to locate David's descendents, the better. It may be then that, when Caesar decreed his census, the entire lineage of David found themselves in the same situation as Joseph -- having to find a place to stay in a tiny, overcrowded village where they knew nobody.
Or... There may well have been some of David's descendants still living in Bethlehem. But imagine it: They must have been completely overwhelmed by the influx of travellers. Bethlehem was a poor, miniscule hamlet at this time, so small that there's no clear archaeological evidence that it even existed (though from documentary evidence it's certain that it did). Several hundred people -- including many with other ancestors besides David -- suddenly descending upon it looking for a temporary place to stay probably created havoc.
Recently a number of scholars (such as C. S. Keene and Ben Witherington III) have pointed out that kataluma (the Greek word translated "inn") actually refers to many different types of lodging places, including whatever kind of guest room Joseph's relatives might have had available. In fact, the recently published Common English Bible translates this famous passage as, "She... laid him in a manger, because there was no place for them in the guestroom," (Gospel of Luke chapter 2, verse 7)
So what Luke may be telling us is that, by the time Joseph and Mary reached Bethlehem, "the guest room in the relatives’ house... would have been filled beyond capacity with all the other relatives who had to journey to Bethlehem for the census."
All they had left to offer the holy family was the stable.