Kruul to be Kynde

This YA novella is the story of Simcha Powers, a high-schooler who is almost compulsively kind - which makes him a target for every bully around. Still, somehow Sim manages to bring some Gandhian skills to bear and usually escape unscathed. As the school year ends, he encounters a pair of aliens from the planet Kynde, who claim that Sim's father (whom he never knew) was one of them - thus Sim is half-Kynde and half-Terran. Their world, which is completely compassionate and caring is under attack by a vicious race of galactic marauders, The Kruul. Having long forgotten how to defend themselves and being existentially unable to commit violence, they wish Sim to return with them to Kyndeworld, to use his combined nature to defeat the Kruul and save the Kynde - without doing harm to any living thing! Sim accepts, and along with his best friend, tech wizard, and all around badass, Hari, and Cog, a cat/dog hybrid escaped from a nearby lab, goes off to save his home world, while remaining true to himself.