In using the “weird sisters” trope, Sutherland develops a supernatural family connection and shared identity for Iris, Vivi, and Grey. The three are linked so deeply, they can sense each other. When Grey goes missing, Vivi says, “I can’t feel her. [...] We’re…tethered, or something. We’ve always been able to find each other” (76). Vivi urges Iris to search for Grey’s energy, but she also comes up with nothing. The sisters’ connection, beauty, and intoxication powers are all strange qualities that make others call them “witches.” Their being called “witches” fits the story’s fairy tale tone too. From flashbacks, readers learn Iris and her sisters have always been connected:

My heart beat in time with hers. The three of us, with the exact same rhythm in our chests. When one was scared, the hearts of the others knocked. If you cut us open and peeled back the skin, I was sure you’d find something strange: one organ shared, somehow, between three girls (121).

Iris’s identity revolves around her sisters, with her comment about their skin foreshadowing their being changelings. Thus, when Grey and Vivi move out of the family home, Iris feels lost without them, as though a part of her is missing.