Ash Ketchum's Age - you do however realize that there can be only one

I don't think ANYBODY ages in the Pokemon world! Ever seen that one episode of Fairly Odd Parents where it was revealed that Timmy secretly made a wish for time to stand still so he'd never age and as such, he'd never grow too old, and in turn, nobody ever aged. I think the same thing happened here! Jirachi was likely an easy cause.

half-sister at best, distant cousin at worse