by TheLionPrince » May 3rd, 2014, 1:32 am
No, they are not confirmed to be related. Zira is simply a delusional follower of Scar and his ideals. It takes more than an "Outsider" nose given Kovu has those distinctive features, but he claims Scar is not his father twice in the movie. However, Zira and Scar having a father-daughter or brother-sister relationship would make for an interesting piece of fanfiction.
Speaking of which, if Zira was Scar's sister, she would also be Mufasa's sister too, making her Simba's aunt. Kovu, Nuka, and Vitani would be his cousins, and given the writers severed Kovu's previously written blood connection with Kiara, it wouldn't be in their vision for Zira to be Scar's sister. In the movie, Zira always calls Scar by his name, and never by a human endearment term like "Dad" or "Father". So, again, it would be good fanfiction material, but not an official relationship in the movie universe.