Their age is stated by an NPC in the WoB when you first go to Mobliz and are introduced to them. The marriage thing is more of an edit for the American audience cause Nintendo had strict policies back then and America still gets pissy about the dumbest things. This was just an edit to make sure the game didn't cause any unwanted attention even though it was poorly done and most gamers don't give a damn.

A lot of censorship back in the 90's were pretty unnecessary.