The magazine said it used "winning combinations of looks, money, and popularity on the Web" to compile the list. Only unmarried royals below the age of 35 were included and the 20 names listed have a combined wealth of almost $60 billion.
The eldest son of late Princess Diana, William, 25, unsurprisingly heads the list thanks to "international intrigue and unparalleled media attention" as well as a "graceful public persona," according to Forbes magazine.
His relationship with girlfriend Kate Middleton, including the "amicable" split announced in April last year and engagement rumors sparked a frenzy of speculation.
William's younger brother, Prince Harry, 23, who received overwhelming media coverage after serving in Afghanistan for some 10 weeks, is in second place with their cousins Zara Phillips, 27, and Princess Beatrice of York, 20, ranking third and fourth, respectively.
Number five in the list is Charlotte Casiraghi of Monaco, the granddaughter of Princess Grace Kelly. A style icon, Charlotte, 22, is known for her "impeccable taste in fashion and her good looks."
An attractive and one of Europe's most eligible royals, Princess Victoria of Sweden, 31, ranked seventh in the top list.
The top 20 Hottest Young Royals:
1. Prince William
2. Prince Harry
3. Zara Phillips
4. Princess Beatrice
5. Charlotte Casiraghi (Monaco)
6. Sheikh Hamdan bin Mohammed bin Rashid al Maktoum (Crown Prince of Dubai)
7. Princess Victoria of Sweden
8. Prince Azim of Brunei
9. Prince Carl Philip of Sweden
10. Andrea Casiraghi (Monaco)
11. Prince Albert von Thurn und Taxis (Germany)
12. Princess Madeline of Sweden
13. Princess Theodora of Greece and Denmark
14. Prince Wenzeslaus of Liechtenstein
15. Princess Tsuguko of Takamado (Japan)
16. Princess Sirivannavari (Thailand)
17. Sheikha Maitha bint Mohammed bin Rashid al Maktoum (daughter of the ruler of Dubai)
18. Princess Iman bint Al Hussein (Jordan)
19. Prince Philippos (Greece)
20. Princess Sikhanyiso (daughter of King Mswati III of Swaziland)
