Just like in Star Wars: The Phantom Menace, there's actually a Cagalli who is Izumi's daughter (and not Kira's sister) that the "original" Cagalli was surgically altered to resemble. After Gundam Seed, Athrun broke up with Kira's sister and started dating the identical appearing but totally different in personality Princess Cagalli. Princess Cagalli confused many outsiders who assumed the scrappy freedom fighter and the Princess were the same person. * Alternatively, the Cagalli of Destiny is a Skrull. * Or a Innovator mole. See below.