What is the theme in Cutting for Stone by Abraham Verghese?

The theme of family bonds is particularly present in the relationship between Shiva and Marion. When the two are born, they are literally conjoined at the head, a connection that is abruptly severed by the cold, sterile operating scissors. Marion claims that this is his earliest memory - being separated from his twin. Throughout their childhood, the two sleep in the same bed, and always find themselves lying head-to-head. Despite the fact that the boys grow up to have very different personalities, Marion still feels connected to his brother.