Middlesex is explicitly related to, though not exactly based on, the mythological stories of Greece. The characters are all part of a Greek immigrant family, and thus readings of mythological stories like than in Ovid's Metamorphoses or Homer's Illiad and Odyssey would be appropriate, as would modern literary adaptations of ancient stories like James Joyce's Ulysses and Eugene O'Neill's Mourning Becomes Electra.
Consider relating Cal's story to novels Golden Boy, by Abigail Tarttelin, and Annabel, by Kathleen Winter, both of which tell stories of intersex coming of age. They are aimed at younger readers and thus less complex than Middlesex, but they will provide a different perspective...