Riley was quiet for a minute. She gathered her blanket all around her. "Paul always loved you, Alice. He knows I know that. I know he loves me, too. But it's different." Alice opened her mouth, but nothing came out at first. "He loved me once. But I think that part is over," she said slowly. "No, it's not. It hasn't even begun." Riley took Alice's bare foot in her hand and squeezed it. "I told him, though, that he better be good to you. When you came along, I said I'd share you, but I told him to remember that you're my sister. I loved you first."
"The Last Summer (of You and Me)". Chapter 20: I Loved You First. Book by Ann Brashares, 2007.