Jacob Sebastian Haugaard Mernild was born in 1972 in Frederiksberg, Copenhagen, Denmark. He grew up in Hjallese, a suburb of Odense. Mernild graduated from in 1993. He was admitted to the 'Teknikum' (College of Engineering), where he was to study engineering. Mernild soon dropped out, however, and instead became a captain in the Royal Danish Army, serving in Kosovo and the Afghan War.