Of course, this being the wishing stone, and the fact that Jon's wish was so vague, the outcome wasn't going to be so straight forward.
While the Fergusons, Blacks, and Meshidas would all be straight forward (meaning that the father would remain the father, the mother would remain the mother, and the daughter would remain the daughter), the Gibson and Meadows families would not. Like the other families, the father and mother wouldn't change, but it was a different story for the children.
The McMillans only had one child - a 17-year old daughter. So each of the five families that were going to change would have the same. Already being 17 years old, both Jon and Biff would remain in existence, but would merge physical traits with their siblings, while also becoming female, and then also taking on the personality traits of Sarah McMillan, of course. Over the course of the next few days, Zoe, Mikey, and Wesley would slowly fade away until it was as if they never existed in the first place. Of course, Jon might still remember them, as he had heard his own (albeit vague) wish. But to everyone else, the female Jon and Biff would be considered an "only child", as would Karyn, Yukio, and Nadine, who already were.
