>>51815503According to bulbapedia:
Red, Leaf, Elio and Selene have 11.
Brendan and May have 12.
Hilda and Hilbert have 14 in B2W2, therefore they had 12 in BW.
So all of them are early teens.
Acording to looker Calem/Serena is older than his assistant (16), but is still to young foe being his new partner, so it seems that is still a middle teen. So, I think that Calem and Serena have 17.
Acording to Cyllene, Dawn and Lucas seems to have 15 or more in PLA, So they also are middle teens at that time.
The other main characters don't have a canon age, but I think that none of then reach late adolescence/early adulthood.
