Where do all the siblings go? One of my earliest book memories was of Ida in Maurice Sendak’s Outside Over There taking matters into her own hands to rescue her baby sister, who has been replaced with a changeling (and, in the movies, the well-named Sarah similarly setting off to save her little brother from the clutches of the Goblin King). The Pevensies ruled Narnia together. Meg Murry and her brother Charles Wallace traveled the universe to get their father back in A Wrinkle in Time, their brothers Sandy and Dennys traveled back to biblical times, and all sorts of other adventures befell their family, as well as the other assorted O’Keefes and Austins and their acquaintances. And I adored William Sleator’s Singularity, in which teenage Harry figured out a way to get out from under the shadow of his twin.

All of that drove home what I knew from my own experience: siblings could be maddening, but they were important.

[Here are 5 SFF books built around a rich, gooey, sibling core.]