"You told Dan, back when she was Dan, that you weren't the same type of witch as me. I think you're right. It isn't really your fault, it's just the type of person you are. When you got your power you could have helped someone, you could have made one of your friends look the way she really wanted, you could have gone to the homeless and summoned them food, you could have healed the sick. You chose to transform your brother against his will. That isn't the first thing a good witch does with her power."
Kat's mother paused. For a moment, she simply looked at Kat, "That's ok, some people just aren't cut out for being witches. Your uncle Jacob is a perfect example. He's a wonderful human being and has done great things with his life, but he wasn't a good witch. That's why my mother made him male."
Kat's eyes opened wide and she started backing away from her mother. She fell off the bed but didn't hit the ground. Instead she floated upwards, then sideways, and found herself back on the bed. She wanted to struggle but was unable to move.
"Kat, calm down and think about it for a moment. Even if this weren't the only way to stop you from misusing your power, it just makes sense. I had a son and a daughter yesterday. I liked having one of each. Now I have two daughters, it only makes sense to turn one of them into a son."
Kat found her voice, "So turn Dan back! He'll thank you for it. I don't want to be a boy. I promise I'll be a good witch."
"Of course you promise. Everyone does. My little sister did before she became Jacob. It doesn't matter what you say, it matters what you do. That's why every witch in our family, on her 18th birthday, is allowed to do whatever she pleases: so we can see what you do, not what you say."
"Mom, please, don't do this. I don't-" and with a wave of her mother's wand Kat found herself unable to speak.
"You didn't even give Dan a chance to protest," Kat's mom said. She pointed the wand at Kat, it glowed with a soft yellow light. Then Kat glowed. Her features changed subtly. Her face changed until it looked male instead of female, but it was still definitely Kat. Her bones shifted to become male instead of female, but the changes were best appreciated by a medical examiner. Her height remained the same. Once the subtle changes finished, the two big ones started. Her breasts deflated, receding until she had a male chest. Her ovaries were on the move, changing as they moved, by the time they pushed out of her body into a newly formed sack they were testicles. The final change was the formation of her, now his, penis.
Kat was still immobile and unable to speak. Her mother looked on, happy with her work. Kat was still immediately recognizable as Kat, but also visibly male. Now she, again, had a son and a daughter, just like she always wanted.