My Girl by Shaw Hart

Winnie Vaughn has only ever wanted one boy; Her best friend and next door neighbor, Theo Vault. She knows that they’re meant to be together. They spend every day with each other and she’s certain that he feels the same way about her. Now, if only he would admit it.

Theo Vault has loved Winnie Vaughn since they were kids. She’s been his neighbor, his best friend, his crush, and the only girl that he has ever loved. He had their happily ever after all planned out but before he could tell her how he felt, their parents threw a wrench in his plans.

Now, Winnie’s not just the love of his life. She’s also his stepsister.