When two cards (for example, Fang, Fearless l'Cie and Vanille, Cheerful l'Cie) are melded, the result is a single permanent (in this case, Ragnarok, Divine Deliverance) that's represented by two cards. If the melded permanent goes to your graveyard from the battlefield, both cards are put into your graveyard. As the melded permanent leaves the battlefield, both of those cards are turned face up again. If the cards are put on the top or bottom of a library, their owner chooses their relative order.