Role Exchanger: brother-sister more fitting roles request

 It was the mid-2000s.

Ethan saw his twin sister Lily's face reflected in the trophy case: her long hair framed by a confident smile that seemed alien yet exciting. He felt a strange surge of confidence as he brushed a stray lock of hair from his eyes and walked over to the cabinet.

Meanwhile, Lila, in Ethan's thin frame, was tinkering with equipment, her fingers now slick with grease.

They were home together when a Role Exchanger arrived and swapped their bodies. It also added new things to their lives; Ethan knew what a Cheerleading routine was from his sister, but he forgot how to play and assemble a computer, which his sister had received. Those were the only things that had changed about their personalities, but officially, there was more.  
This was because Lila was generally more of a tomboy and disliked girly things, while Ethan had a slight weakness for them. They both also hid their gender preference, and after the role exchange, they retained their old orientation. This meant Ethan was now a woman who liked boys and Lila a man who preferred girls. 

And although they preferred to stay in their own bodies, you don't look a gift horse in the mouth. So they decided to go with the flow. Hours turned into months, and the siblings learned to navigate their own worlds. At the same time, they managed to stay in each other's circles of friends despite their gender transition. Lila quickly found a sweethearts among her friends, but Ethan preferred to keep things on a friendly level.