Viola Cesario and the Polyjuice Potion

The Cesarios are a pureblood wizard family. Viola Cesario, unfortunately, was born a squib; the first ever in her family. Despite not having any magical prowess, she has an obsession with magical theory and has been a star Quidditch player since she was three. But since she doesn't have magic, she's not allowed to play on a real team. In order to avoid any scandal, she's been annually shipped off to a muggle boarding school by her parents.
Her twin brother Sebastian, on the other hand, goes to Hogwarts and was sorted into Gryffindor. But he has no interest in magic. His dream is to live as a muggle, to learn their technology and culture. He has no interest in the magic and world he grew up surrounded by.
Viola and Sebastian often mused about switching places, but it was impossible.
Until they discovered the polyjuice potion.