Gjert Wilhelmsen and his family own an estimated 7% of publicly traded Royal Caribbean, the cruise ship company that his brother Arne (also a billionaire) cofounded in 1969. Holding company A Wilhelmsen A S, owned by Gjert and Arne and their families, is active in real estate, shipping, retail and asset management. Gjert got his degree as a naval architect from The University of Trondheim.