Children of the Lamp is a series of four books that deals with a family of dijinn (known casually to Western culture as genies) who disguise themselves as humans, but can still grant wishes to humans. It centers around two young dijinn twins, John and Philippa Gaunt (nice nod to the Plantegenets there), and their challenges adapting to the world of magic and wish-granting. While honing their skills, they must often confront the powers of evil in order to keep the balance between good and evil. Their adventures take them from their childhood home in Manhattan to the snowy reaches of Nepal.
Yes, it sounds more than a little like Harry Potter, albeit with more globe-trekking. Hopefully, that's just a misconception born of Wikipedia and not a reflection of the actual books. Has anyone out there in Cinematical comment land actually read them, and can fill us in?