>>27358844Going to have to disappoint you here pal.
But the only time age has EVER been stated IN-GAME (Not in any side media or guide, or anime) was actually in OR/AS, where your protagonist is stated on one of the tv segments to be 12 years old. So May is not "At least 13", but actually exactly 12.
It's very highly likely that all protagonists from Gen 1-4 are that age, save for Red who is widely accepted to have been 11 because of the Guidebook and the Manga.
Gen 5, they tried to mature the series a little, and the protagonists Hilda/Hilbert were explicitly said by their creator to be "older than the other playable characters", with the Manga listing them as 16 to reflect that.
Emma, in Gen 6, was described as being 16, so you can suggest Serena/Calem are that age. Rosa/Nate are a little younger, with the Manga listing them as 14. You can say "Manga isn't canon!" but I feel like this is very significant, because of Hilda/Hilberts older ages. There was a conscious decision there to acknowledge Rosa/Nate as slightly younger, because Hilda/Hilbert were part of a much more mature story, the most mature attempt at a story Pokémon ever did.
Sun/Moon appear to be returning to the younger 12-ish year old characters, reflecting the lighter feel and storytelling of the games again.