Robert Lebersorg was born in Etterbeek, near Brussels, in 1939. He began his career as an independent illustrator in 1961. He made several vertical comic strips for Le Soir, which he signed with only his first name. He also made the drawings for a couple of stories in de series 'Les Belles Histoires de l'Oncle Paul' by Octave Joly for Spirou magazine. He found employment with the Dupuis art studio, where he assisted Serge Gennaux on the layouts of the publisher's magazines. He also made illustrations for Bonnes Soirées during this period.
It was there that he met Raoul Cauvin, with whom he created some of the few realistic Cauvin stories. They started out with some stories for Le Soir Jeunesse in 1969 and 1970, 'Luc de Tarente', 'Alerte aux Iroquois' and the western 'Prime pour une Couronne'. Some of these stories were later reprinted in Samedi Jeunesse. Lebersorg and Cauvin then collaborated on a couple of 'Musti' gags for Bonne Soirée in 1970 and another historical realistic story, 'Fontenoy', that was published by Archers in 1987. Specialized in historical comics, Lebersorg then drew 'Wallenstein: Les Années du Diable' from a script by Diego Couturier for Le Lombard in 1991.