TIME The Science of Siblings

For many of us, the relationship that we have with our siblings is one of the defining ones of our lives, and they play a powerful role in shaping who we become. In many cases, these relationships are incredible bonds that will last a lifetime. Brothers and sisters are our collaborators and co-conspirators, our role models and our cautionary tales. They are our protectors as well as our tormentors. There are alliances and feuds, loyalties and betrayals. Slights are remembered and favors are banked, but no matter what, the relationships are many times the longest and most consistent of our lives.

Now, in this special edition from TIME, bestselling author Jeffrey Kluger (Apollo 13, The Narcissist Next Door) brings you the latest insights on the many facets of sibling dynamics: birth order, favoritism, fighting, blended families, and more. Examining the most-recent work from psychologists, sociologists, anthropologists, and biologists, The Science of Siblings brings you the latest insights on the many facets of sibling dynamics and what it can teach all of us.