Although the game prompts you to create a new Sim as soon as you can you will discover that once you beging the creation process there is no way you can back out and you will be stuck with it because there is no actual way to delete a Sims. The only way you can remove the unwanted Sim from your playable family is via retirement or if one of your friends asks your Sim to move to their house. For some reason EA has refused to address the issue of deleting Sims on The Sims Mobile on their forums.