Unspoken / Brennan, Sarah Rees

Kami Glass is in love with a boy she's talked to in her head since she was born into her small English town. Soon strange things begin happening in town, and the Lynburn family who ruled the town a generation ago, and who left without warning, have returned. Kami discovers that her town is hiding a multitude of secrets, and a murderer. The key to solving the mystery lies with the boy in her head who she thought was imaginary, but who turns out to be real and dangerous.

The twin Lynburn sisters, whose family has owned the sinister manor that overlooks Sorry-in-the-Vale for centuries have returned with their sons, one of which looks remarkably like the imaginary boy in Kami's head, who she is in love with, but with the twins return, strange things begin to happen in Kami's small sleepy town.