[@Snarfulblast]

You're missing the point man. There's a difference between being trained by a human and being trained by a Pokémon. Humans are the only ones that can mega evolve Pokémon. Ergo, Jean cannot mega evolve Carl. 

In other words, in order to settle things, I suggest either making another human character and putting him and Carl on a separate team together, thus making him eligible to mega evolve at this point in time, or simply edit your post to where it's either only Zera or Carl that is mega evolved.