Traci Harding - Tablet of Destinies (Celestial Triad #2)

The second book in The Celestial Triad takes Tory and Maelgwyn into the realms of the Devachan, the Fourth Dimension. They and their clan have had many peaceful years on the planet of Kila until Tory's new twin babies, only a few days after their birth, are switched with changelings ... the babies now exhibit all the characteristics of fairy folk and, as with all deva infants, are neither male nor female.

Tory seeks the counsel of the Tablet of Destinies and is told that the changelings are the first of the Devachan to venture into human existence, and that her twins are the first humans to choose to experience the world of the Devachan ... and all the babies are psychically linked. To reclaim their children, Tory and Maelgwyn must journey into the fourth dimension.