Rift Runners, book 1: The UndividedJennifer Fallon2011

The Undivided are divided. The psychic twins, Ronan and Darragh, have been separated by the traitor Druid, Amergin, who has kidnapped Ronan and thrown him through a rift into another reality. Now time is running out for Darragh. If Ronan isn't found soon, they will both die. But his twin brother is lost in a reality where Druids are legend, and there is no magic. Somehow, before the Autumn Equinox, they must find one young man in a world of six billion people...

Meanwhile, Ren Kavanagh has no notion of where he comes from. He is plagued by strange injuries that appear from nowhere and everyone is convinced he is deliberately harming himself for attention. Then he meets the enticing and mysterious Trasa, and before he can figure out how it happened, he is in serious trouble - arrested for arson and possibly murder.

Rescue will come from a completely unexpected direction. Ren is about to discover more about his origins than he bargained for, meet the twin brother he never knew he had, and discover nobody is what they seem, especially his new friend, the half-faerie, half-human Trasa... Amergin's daughter.