I'm looking for a book about stepsiblings; I can't remember the title or author.
I'm looking for a book where the female protagonist's mother marries the male protagonist's father when they were children. They are both only children, and the male protagonist suffered abuse in his childhood. The female protagonist is around 17 or 18. He gets her to help him with his homework. He goes into her room and finds her, I think, in a bathrobe. He sees her skin, and I believe at a school party, he confesses his love to her and kisses her. When her parents find out, the protagonist's mother sends her to live with an aunt and two cousins. I think there's a Fourth of July party, and the aunt takes her and her cousins to the party. It takes a while, but the male protagonist goes to get her and sends her a message to meet up. When she's about to leave, one of the cousins or the aunt sees her, but she says she's going to get something and then goes outside, and he picks her up in his car. They leave the country; I don't remember which one, I think it's somewhere in Europe. But the person who helps the male protagonist leave the country is an ex-girlfriend, and they meet in a public place, I think at a Starbucks. She has connections to help them leave the country. And that's also why it took the male protagonist a while to go and find the female protagonist. And when they're in that country, he takes her to a park or garden, and there the male protagonist encounters the people who abused him as a child. He manages to locate them and discovers they still have children in their custody. The male protagonist decides to work with the police, and during the confrontation, he or she is shot.