I also hope it's sisters just so we can get some kind of Shakespeare level love triangle going on. Noctis, crown Prince of Lucius, arranged to be wed to the prominent noblewoman Lunafreya Nox Fleuret of Tenebrae. Noctis, however, longs for the affections of Lunafreya's sister Stella, who for unknown reasons has become an agent of Niflheim - the nation that laid waste to Noctis's home.

Whether it be in game or in fanfic this is gonna happen one way or another