The U.S. business magazine said that in compiling its Top 20 list, it took into consideration family wealth, as well as the individuals' Internet and media presence.
Only unmarried royals under the age of 35 were considered.
Coming in at No. 2 on the roster is William's younger brother, Prince Harry, followed by Britain's Zara Phillips, daughter of Princess Anne who didn't want her children growing up with formal titles, at No. 3; Princess Beatrice of York fourth and Monaco's Charlotte Casiraghi at No. 5.