Curse of a Dragon Heart - Dragon Descendants Series, #0

Possessing a magical ability is dangerous. Sixteen-year-old Jason struggles to care for his younger brother, Charlie, while concealing his growing fire power. Months ago, their parents were conscripted into the Great Wars and drained of their magic by the war mages. Now they're dead. Desperate for food and shelter, Jason volunteers at the army camp despite the risk of discovery. While dragons soar overhead and the sounds of battle fill the air, Jason keeps his magic under control.
Until a plague sweeps through camp, catching him in its deadly embrace. Terrified that Jason will die, Charlie makes a dangerous pact with a war mage, which unleashes a spell that saves Jason and kills a dragon. Now bound to the dragon's family, Jason embarks on a quest to find the dragon keep and warn them of the mage's curse. But the boys' journey is fraught with danger. Jason's magic has transformed into something he can't control, something monstrous.
He must rid himself of the inferno within, before he harms Charlie and destroys the dragons he seeks to protect.