Mother Mary is NOT an important figure in the bible. Her name is probably mentioned 12 times in the Holy Scriptures. The only important account we have of her, is the message which she received about the birth of Christ. The 2nd message, fleeing to Egypte, went to Joseph and he informed his wife.
Right, she gave birth to Jesus, but isn't really significant aside from that. Anyway, the nativity scene isn't really about "Christmas", as "Christmas" isn't a Christian holiday.
Right, and the leading nation was Rome, so his parents were leading a secret life not to endanger christ, his brothers and sister, waiting for his adulthood and mission. We read again about mother Mary, before the crucifixion of her son, burial and short thereafter. The lineage of Joseph is mentioned, so we know that Christ descended from King David and King Solomon.