deduce the age of the subjects:
     all s: subject |
            s.deducedage = (photo.s.age, photo.deduceddate + s.deducedage)[1]
                                    
One neat trick would be to calculate relative relationships: if the viewer is x and the subject is s then what is s to x ( great great grand uncle or even the more verbose - your father's father's father's brother)
This calls for a Prolog engine perhaps
Possibilities include