One True Impossible Pairing

Seriously, why is my fanficcing OTP apparently Catria/Marth?  It doesn't happen.  It can't happen.  The amount of canon-warping to make this even possible is tremendous, confining it to the land of utter AUness or sometime well after the games.  And I don't have a problem with that, as I'd rather write about adults than teenagers anyway, but it still calls into question as to why I've latched onto what is, canonically, a teenager's unspoken crush on her superior.  Unspoken-- and unrequited.