The Mistmantle Chronicles Book One-Urchin of the Rising Stars by M. I. McAllister*

As far as everyone knows, Urchin descended upon Mistmantle, an island,  as a baby squirrel from the sky.
Urchin thrives under the care of Apple, another squirrel, plus various creatures in Anemone Wood.  Captain Urchin, one of the three captains serving King Brushen, takes an interest in him.  Eventually he is Captain Urchin's page.
Then an evil pervades the island and patiently deceives many of the creatures.  Captain Padra and others,  true to maintaining the lives and goodness on Mistmantle, however, counter the evil with secret rescuings and plans.
-Borrowed from the library (but may be a series we buy).
*Highly recommend (please see warnings/points to discuss).

Warnings/points to discuss: murder (killing the prince baby, villain had killed one of his siblings as younger creature), violence, killing of deformed/weak baby creatures, use of alcohol/medicine to drug/control the king

I read this aloud to my two boys (ages 9 and 7) and they loved it.