Blood is thicker than water. I didn't understand that expression when I was a kid. I only knew that I was closer to my brother Seth than to anyone else in the world. He was the calm to my storm, the light to my dark. We were tied to the rest of our complicated family by bonds beyond blood-love, loyalty, convenience-but as it turns out, the pull of blood is strong. Maybe even strong enough to tear me away from the person with whom I shared my very...