[pepsionice]

Well....no one has ever given an age to Joseph or Mary. It’s possible that she was 17.

[Morgana]

I’ve always been told she was about 14!!

[xzins]

Since elizabeth was old, and a cousin of Mary, Mary could have been older than many think

[Varda]

I like that guess too. I studied marriages similar to what’s described (marriage made when the girl is a child but she doesn’t live with her husband until later) so I’ve imagined she was about 17 or 18
(average for those marriages).