[quote="Immortal Lioness"]Thelionprince- You read correctly. Disney changed it to Mufasa and Sarabi being married, only having one cub Simba.
It's true that Sarabi was mean't to have sister who was going to be the mother of Nala. But that as you stated was during the production of the king of the beasts, before it became the lion king.[/quote]
I knew I wasn't reading wrong. Thank you, Immortal Lioness!
[quote="Immortal Lioness"]Shani was going to be the name of Simba's cub. But they changed it because shani means devil I think... basically a evil meaning behind it. So kiara they named her

Well if Simba had a brother or sister that would have changed the storyline completely. Scar would have had to scare away- kill the pair of them. I'm glad he didn't have a sister or brother though

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I think you're slightly mistaken. Shani means "curiosity, novelty, something unusual" in Swahili according to this
Swahili to English online dictionary. The name, Shetani, means "devil" in Swahili so they changed to Vitani so it's a portamanteau of "demon of war" or "ducks" as one source I remember said.
And, if Simba had a sister/brother, it would be another obstacle (and more work) for Scar and the hyenas to get rid of in order to usurp the throne. Also, Scar and the hyenas would have to craft a really good plan in order to make Mufasa, Simba, and the sister/brother's death look like an accident so no one will raise eyebrows as to how three members of the royal family just suddenly died. Finally, it would inflict more emotional pain on Sarabi when she thinks her whole family is dead.
It'll be an interesting fanfiction since it can't be a fact to say Simba's sister/brother survives, dies, or get separated from as a result of Scar's death traps he set up from them. Who knows? You can kill off Simba, and let the sister/brother live. Maybe, Simba's sister/brother will be an even more closer friend to Nala, and the sister and Nala could chat about girl stuff. The rest of the story is left to you. There's just so many possibilities.