After a short pause for wondering what to do, you take your decision: you will be the last girl here! So, you point your wand to your step-sister Tiffany and make your wish, casually thinking how could be to have a brother instead a sister.. and something magical happened.
A bolt hits your sister Tiffany, and she started to change!
First, her breast deflated but the entire chest expanded.. a male chest?! The dark hair growing over makes that unmistakably true, as the fact that her arms and legs are thickening and covering as the same way with hairs.
Then, her face. Her hair shortened, leaving her beautiful and long blond hair in a crew cut. Her jawline becoming more angular, her eyebrows thicker and bushier, and her chin and cheek covering with a stubble, and on growing beard, indeed.
And last, a big bulge pushed in her crotch area, while her shorts and her t-shirt adapted to her new frame.
Your step-sister Tiffany's gone, now here is Tim, your step-brother!
Then, you heard a knocking on the door.