Even though it was common during that time for a man who was around 20 to marry a 14 year old. I don't see any evidence to suggest Joseph and Mary were any different.
Also, when I was just 6 years old a 15 year old girl used to fool around with me sexually... and I honestly can't say it was coercive. Now she was truly a pedophile, and while I'm not saying what she did was right... I just don't believe she should have been put in prison for it.
The law is a blunt instrument and many innocent people with perfectly healthy relationships in their teens have had their lives ruined due to the hysteria surrounding this subject.