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.
Gerhard C. Kallevig took commercial education in London and Hamburg, stayed in Fredrikstad and Northern Sweden and also worked in Germany for one year before starting his own trade firm in 1900. The firm traded in wine and timber, and sold marine insurance. He then started the companies Automobil-Compagniet in 1908 and Aurora Auto Company in 1911, and was a pioneer in establishing bus routes in Norway.
He established the routes Oslo–Hønefoss, Fagernes–Lærdal, Stalheim–Voss–Eide and Elverum–Trysil.
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. He sold Aurora in 1931.
In 1911 he also established the insurance company Forsikringsselskabet Viking, and worked as chief executive officer In 1926 the company acquired Norsk Reassuranceselskab and Forsikringsselskapet Minerva, and Kallevig later bought a majority in Kredittinstituttet.
In 1956 he retired as chief executive of Viking.
He continued as chairman of the supervisory council until 1961. He died on 9 August 1964.
He was a founding member of the gentlemen"s skiing club Saskatchewan Fram in 1889, of which he received lifetime membership in 1961. He was also a member of the exclusive Det Norske Selskab and Christiania Jægerklub av 1873 clubs.
