The Bible does not say how old Mary was when she got betrothed to Joseph or when she got pregnant with Jesus. The Bible does not tell anything about Mary’s parents or how they raised her. This episode was created by considering the customs and conditions that existed in Nazareth during this time period.
At the time of Jesus’s birth, Nazareth was a small village in the middle of nowhere—it wasn’t even mentioned in the Old Testament. Matthew 2:23 records that the prophets said Jesus would be called a Nazarene, but we have no record of those prophecies. When Jesus started recruiting his followers, Nathaniel said, “Nazareth! Can anything good come from there?”
At the time of Jesus’ birth, the nearby town of Sepphoris was not yet important, and the city of Tiberias on the Sea of Galilee had not been built. Nazareth was perched on a hillside overlooking the important trade route running through the productive Jezreel Valley, but Nazareth was separate from them.
At the time of Mary’s pregnancy, Nazareth likely had a population of a few hundred, and probably had public water source which would have been used for civic and religious purposes. All of the residents would have been Jewish. Very likely the Nazarenes would have had close ties with those in nearby villages, such as Cana.
During that time, having children was of utmost importance. Marriages determined family lines, solidified family ties, and aided in establishing economic prosperity. Parents of males would be focused on making sure their sons were able to provide economically for their families, and parents of females would be focused on making sure their daughters were virgins and would be good mothers. In modern times, that all sounds antiquated, but there was an additional important reason for all that.
Inheritance and religious factors made it imperative to know whether a first-born son actually belonged to the father, and the only way that could be assured was for the wife to be a virgin at the time of marriage, and for her to remain faithful until the first pregnancy. It was impossible for parents to be too overprotective of their daughters’ sexual purity and reputations.
Against that backdrop, try to imagine how Mary’s parents must have felt and reacted when she announced her pregnancy.