Hi ksd
If by "front seats" you are referring to the Bulk Head Seats (which are where you get more legroom etc) then yes, I believe you do have to be over 16 (may even be 18) and in good health. This is because these seats are situated by the doors, and should there be any reason, where the safety slides go down for Emergency Exits.
The people who want these seats normally have to be fit and able.
HTH