>>47232420The official lore states people become eligible for their trainer license on their tenth birthday, and that once someone has their license they’re considered legally an adult. Both for cultural and pragmatic reasons, we can assume the vast majority of people who want to become trainers acquire their license as soon as they’re able to. The Gen 5 and 6 protagonists were explicitly stated to be older than usual, but if we look at their physical development they only appear to be around 14 or 15. The other protagonists (save for the Gen 3 remakes who were aged up to match the XY protags) all are of the physical development stage of children around age 11.
They’re quite young, which makes sense considering the original target audience was boys around age 7-12.