To his family, he’s Christopher; to the world, Ashton Kutcher. Five minutes older than his twin, Michael, Ashton had always been his protector. Michael was born with underdeveloped lungs, later diagnosed with cerebral palsy, and often endured bullying. Ashton stood by him through every challenge, vowing more than once that he wished he could take his brother’s struggles on himself. But nothing prepared them for the crisis that hit when they were 13.

Michael was diagnosed with viral cardiomyopathy, his heart swollen to four times its normal size. Doctors gave him weeks to live—until sudden cardiac arrest cut that to 48 hours. He needed a transplant immediately. Desperate, Ashton told his parents he was willing to give his own heart to save Michael’s life, even considering ending his life so surgeons could use it. Minutes before time ran out, a matching donor heart became available, and Michael survived the surgery.