Warbler said:

yeah, 12 is too young to marry, so is 16. Why the difference for males and females? Why can females marry at a younger age than males?

I really don't know. I would say it is some law not reviewed for a long period of time.

Maybe something like "women shall old enough to give birth to child and men shall be old enough to give their family some proper shelter", but I have to guess (maybe wrong) on that.

I don't know how far Iran got it, but there was a try to bring down the age for a girl to be marriaged to the age of 9 in Iran.

Personally I don't need to discuss it, because I think the age of 18 is a reasonable age, maybe with some special decided exceptions down to 16 or 17. (Some people at 16 are more reasonable then some other at 25... ) I just wanted to show a delicate topic wich was not completely included in my "love is the foremost important part in a relationship" because the matter of age is something which can't be lighly put (or more to say "ignored") under such simple sentence.