This is what I learned in Catholic school as well, except I never heard Joseph was her uncle. But it focuses my problem. The story itself, as you quote it, states that Mary was the first to have chosen this path. Why would a child be allowed to make such a choice, when it was completely outside the tradition of Israel? If they knew she was to be the mother of Messiah, fine, but they did not, or one of them would have told Herod (it was barely three years from this incident when the wisemen asked about the situation). I do not trust the story, because it represents the wisest men listening to a young girl, perhaps 6 or 10 years old, and asking that she be allowed to remain childless, and hence, a reproach in Israel. The story you have quoted seems to begin after they had made the decision to respect the kid's wishes (and that's all she was to them at this time). Can you answer why they allowed such age old traditions to be violated?