Prince William revealed that he wants to have two children with his wife Catherine, British media accompanying the royal couple on an Asia-Pacific tour reported.
"Someone asked him how many children he would like to have, and he said he was thinking about having two," Corine Ackerman, 17, a student at the British-standard Tanglin Trust School in Singapore, was quoted as saying.
The Press Association said William had spoken candidly in the past about starting a family with Kate but had not commented about numbers.
The royal couple, on the second day of a tour celebrating the 60-year reign of Queen Elizabeth II, were chatting with well-wishers at the Gardens By The Bay botanical park, Singapore's newest tourist attraction.
Asked what superpowers he wished he had, William, dressed in a dark suit, replied "invisibility", the Straits Times newspaper quoted him as saying.
When asked the same question, Catherine, one of the most photographed women in the world, quipped: "I'd pick invisibility too so that William can't sneak up on me."
The chat with fans at the park was followed by a visit to a sprawling Rolls-Royce jet engine factory.
In a gesture aimed at boosting British industry, the couple unveiled the first Trent 900 engine made in the plant to Rolls-Royce executives, corporate guests and employees waving British and Singaporean flags.
The engine powers the Airbus A380, the world's largest passenger plane, and Rolls-Royce built the plant in Singapore to be closer to customers in Asia, the world's fastest-growing aviation market.
"Here is cutting-edge aerospace technology developed by one of the United Kingdom's great global companies," William said at the 154,000 square-metre complex which opened in February.
The plant, which also includes research and training centres, was built at a cost of Sg$700 million ($570 million) and employs some 500 people.
William said British firms had invested a total of 25 billion pounds ($40 billion) over the years in Singapore, a former colonial trading outpost that has become one of the world's wealthiest societies.
The couple also visited a community called Queenstown, named to mark Elizabeth II's 1953 coronation, drawing a crowd of more than 500 around a playground where they were treated to cultural and sports performances.
"She looks like a model," said Singaporean student Grant Hor, 12, who took time off from school and showed up with his mother Yan.
To the crowd's delight, William, who had taken off his tie and unbuttoned his shirt collar, tried playing capteh, a traditional game involving juggling a shuttlecock with one's feet.
William and Catherine will stay in Singapore until Thursday and proceed to Malaysia, where they will tour the capital Kuala Lumpur and Sabah state.
The pair will then fly to the Solomon Islands, an impoverished former British protectorate north-east of Australia, before a final stop in the tiny nation of Tuvalu, where the tour will end on September 19.
Queen Elizabeth is head of state in the Solomons and Tuvalu, both of which are members of the Commonwealth, as are Singapore and Malaysia.