There actually isn't allowed to be two victors. In the 74th Games, they said there could be two so that Katniss and Peeta would work together and keep the whole "star cross'd lovers" thing going. Once it was down to the two of them, they reinstated the original rule that only one person could live. However, when they both attempted suicide, they said that yes, they both could win, because they'd rather have two victors than none at all. That was the only Games were two victors were ever allowed. In every Game before, and every Game after, even if the final two were from the same district, only one was allowed to win.
So yeah, two victors is a bad idea. One Game, one victor.
