Many think that the elements of Christ's birth are a unified story, but they are drawn from two separate accounts in the gospels of Matthew and Luke, according to nativitysets.com.
The Nativity of Matthew
Matthew, the first book of the New Testament, begins with a genealogy of Christ and moves into the nativity story, focusing on King Herod and the journey of the three kings.
Matthew writes about the three kings coming from the east, following a star that proclaimed Christ's birth. The kings visited Herod before following the star to Bethlehem.
Angered by the story of a new king, Herod ordered that all children younger than 2 living in Bethlehem be killed. Joseph was warned in a dream and fled with the family to Egypt. They eventually settled in Nazareth.
The Nativity of Luke
Luke, the third book of the New Testament, contains many of the elements of the traditional nativity scene. It begins in Nazareth, which the holy family leaves to go to Bethlehem because of a tax census.
Because of the number of travelers in the city, Joseph and Mary seek shelter in a stable, because they can't get a room at an inn. Christ is born in the stable and placed in a manger, which is used to hold livestock feed.
Luke's narrative also includes a field full of sheep, and an angel informing the shepherds of Christ's birth. The sky is filled with a multitude of singing angels. The shepherds hurry to the manger in Bethlehem.