After Jon entered the cabin, he was nearly blinded by an intense white light. Instinctively, he lifted his hands up to his face, but there was something wrong. When his hands touched his face, they felt more delicate than normal and he could have sworn that his nails were longer as well. What was happening?
When the light dissipated, though, it was very clear what had happened, although seemingly impossible. The reason his hands felt different was that they were girl's hands.
Jon looked down at his body hesitantly, not wanting to see what else had happened to him. Just as he had feared, he was a girl. He was even wearing the female equivalent to his clothing.
He looked around at the rest of his family and saw a 14-year old Goth boy, a 10-year old girl, and a man and woman. They had all changed genders. But it wasn't just their bodies that had changed, it was also their clothing.
Jon looked back down at himself and gently squeezed one of his new breasts through his tight baby-T shirt. They were definitely real and the feeling he got from touching them was unlike anything he had ever experienced before.