Sebastian Morgenstern, born Jonathan Christopher Morgenstern, was the son of Valentine Morgenstern and Jocelyn Fray and the older brother of Clary Fairchild. As a result of experiments done on him by his father, Sebastian was a Shadowhunter born with demon blood. After a stint in Alicante when he posed as Sebastian Verlac, he later decided to keep the name Sebastian as an act of defiance against his parents. Shortly before his death, however, he reclaimed the name Jonathan during his last few moments without demon blood.