He was born in Kristiania as a son of director August Kallevig (1851–1924) and Wenche von der Lippe Mowinckel (1857–1939).
On the maternal side he was a great-grandson of Bishop Jacob von der Lippe and a first cousin once removed of Gerhard Gran.
[1] Gerhard C. Kallevig took commercial education in London and Hamburg, stayed in Fredrikstad and Northern Sweden[5] and also worked in Germany for one year before starting his own trade firm in 1900.
He was reportedly the fifteenth person to get a driver's license in Norway, and the first to cross the Dovrefjell mountain range by car.
[1] In 1926 the company acquired Norsk Reassuranceselskab and Forsikringsselskapet Minerva, and Kallevig later bought a majority in Kredittinstituttet.