Born under the star sign of Cancer, Prince William and wife Kate Middleton's first child "should grow up to be a sensitive monarch with a streak of iron", The Daily Express newspaper reported quoting astrologer Patrick Arundell.
This combination of caring and tenacity, along with leadership skills, could be ideal characteristics for the future King, the report said.
About half an hour later, he would have been a Leo, it added.
"With Cancer people, though they appear to be quite soft, they can be quite tenacious. They are also family loving and adherent to trends and traditions. They are caring and loyal," Arundell said.
William, born on June 21, is also a Cancerian as was his mother Diana, whose birthday was July 1.
Other famous names who share the star sign include South Africa's anti-apartheid icon President Nelson Mandela, actor Tom Cruise and Edward VIII.