I don't think they're related, unfortunately. If they were, their size and body structure would've been similar, like legendary birds, beasts, kami, Swords of Justice (excluding Keldeo, since it originally wasn't a part of the group), all other trios. Mega Latias and Latios seem to be in the games, too, but they just haven't been officially confirmed, though. ): Hope they do it soon. Also, this makes me wonder if there are other mega-evolutions out there? Personally, I'd really like to see mega Typhlosion and Dragonite, haha.