He heard a voice in his head with the reply
"in this reality you have two strong personalities, one a boy and one a girl, the personality is so strong that your body changes when the other one takes over, most people outside your family don't know that you and your sister are the same person."
"What the? That's so strange."
Just then he felt a mild head-ache and a voice in his head.
"Jon you know I'm going to the mall tonight with the girls, stop pushing me out."
Jon wasn't sure what to do other than relax, and when he did so everything became hazy for a few moments and his body started moving on its own, and it changed.
Moments later instead of Jon standing there it was a girl that looked Similar to Jon dressed in his clothes.
To Jon it was like he was a passenger, he still had all his senses, he could feel the weight of his/her breasts and the emptiness in his/her crotch but couldn't control anything.
"Oh and Jon... I didn't want to tell you this until I was in control again, but I've got another date tonight, and I'm thinking of going all the way... Hope you don't mind."