Time passes in the Pokémon World, so Ash does age. It's just a matter of knowing at what rate ...
Locking this topic because it suits best in the anime section. Moreover, it's a very old topic that had probably been touched on occasionally, even there.
Thanks for reading.
“A single soul can uphold a standard far above the low threshold by which the world measures itself.”
Latest Review: Dark-type Award Ceremony
Bonus articles: Mega Evolution Candidates (Part 7) -- Generation 6 Pokémon (07/12/2013)