Harry and Jaqueline Potter: Opposites of the Hall

I will not write about anything prior to their fifteenth birthday, so make sure you read the original books first! In this story, Harry Potter has a twin sister named Jaqueline (called Jaqui, or Jax by Harry and her friends). In this story, everything is the same pretty much for Harry, but I added some things into his life to go with how life for his sister is. His sister is the main character also. Harry and Jaqui are very close throughout life, until they get Sorted into their Hogwarts Houses in fifth year (the Dursleys somehow stopped the letters for four years, but they learned with Ms. Figg). Harry expected Jaqui to be in Ravenclaw since she was the smart one. But after he was made a Gryffindor, and she was made a Slytherin, they become distant with each other, especially when she falls for the youngest son of Voldemort... Mattheo Riddle. And it gets even worse as she and Mattheo (who she calls Theo) end up getting into a LOT of trouble together as their bond strengthens, and he begins to tell her to defend herself. And one day, Theo and his brother Tom Jr. tell Jaqui the whole story of what went down the night her parents died. And Jaqui starts having visions and random power surges... she's the real chosen one. And as she figures out how to control her powers, she also stops denying the truth... Her parents weren't good people, and they might not even be her parents either...

Written in third person, from Jaqui's side mostly, and a few chapters from Harry's side and Theo's side.

(Side Note: Harry tries to get Jaqui to believe that everything the Riddle brothers are telling her is lies, until eventually he believes it himself.)

Who do you think her real brother is? (Hint: he's mentioned more in this book than he is in the originals.)