Nobody affects us as deeply as our brothers and sisters—not parents, not children, not friends. From the time we—and they—are born, our siblings are our collaborators and co-conspirators, our role models and cautionary tales. They teach us how to resolve conflicts and how not to, how to conduct friendships and when to walk away. Our siblings are the only people we know who truly qualify as partners for life. In this groundbreaking book, renowned science writer Jeffrey Kluger explores the complex world of siblings in a way that's equal parts science, psychology, sociology, and memoir. Based heavily on new and emerging research, The Sibling Effect examines birth order, ongoing twin studies, genetic encoding of behavioral traits, how emotional disorders can affect—and be affected by—sibling relationships, and much more. With his signature insight and humor, Kluger takes big ideas about siblings and turns them into smart, accessible writing that will help anyone understand the importance of siblings in our lives.