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>If you talk to an out of the way NPC you find that the reason Trevor wants to be a trainer is because his parents abandoned him and his sister just to go off and travel the world, and presumably he wants to go find them
>This is never touched upon in the main story or ever expanded on besides those few lines of dialogue with that one NPC
Really, I'm just dissapointed in the characterization of your group of friends on the whole. Platinum and the Gen V games all actually had pretty decent characterization, especially for Pokemon.