Greystone secrets

"he Greystone kids thought they knew. Chess has always been the protector over his younger siblings, Emma loves math, and Finn does what Finn does best--acting silly and being adored. They've been a happy family, just the three of them and their mom. But everything changes when reports of three kidnapped children reach the Greystone kids, and they're shocked by the startling similarities between themselves and these complete strangers. The other kids...

Told from separate viewpoints, as evil forces from the parallel world invade their home, the Greystones, their doubles, and friends must return to the alternate dimension to save both worlds.