Prince William will come to Wales to learn Welsh - just like his father.
Prince William has hinted he will play a role in Welsh life
The prince is due to spend six months, probably in Aberystwyth, when he finishes his current university course at St Andrews in Scotland.
The revelation was made by royal biographer Brian Hoey speaking exclusively to BBC Wales.
"I happen to know that, when he finishes at St Andrews University, he is coming to Wales for at least six months, to learn the language," he said.
"He wants to learn that in preparation for the days when he of course also becomes Prince of Wales."
William started to learn Welsh at Eton in 1999, after Prince Charles said he was anxious for his eldest son to become fluent in time for his investiture as Prince of Wales.
The Queen and Prince Charles addressed the Welsh assembly
At the time, he had William take extra lessons from Ffion Hague's sister, Manon Williams.
Last week, it emerged that William has decided to teach himself Swahili, after his experiences in Africa.
Glyn Davies, AM for Mid and West Wales, and a committed Welsh learner, has welcomed the news.
"The Welsh language is the cultural treasure that makes
Wales unique," said Mr Davies, who reached the final of the Welsh Learner of the Year competition of the National Eisteddfod last week.
"I have become obsessive in my desire to strengthen and promote its use."
On Wednesday Prince Charles addressed the Welsh assembly in Welsh.
The Prince of Wales was accompanying the Queen and the Duke of Edinburgh on an official visit to mark the start of the new Welsh assembly term.
I knew I would be seeing a lot of Wales in the future,
Prince Charles spent three months studying Welsh at the University of Wales, Aberystwyth in 1969, before his investiture as Prince of Wales.
Prince William - who is second in line to the throne - is currently halfway through his four-year degree studying History of Art at the university on the coast of Fife.
After he leaves St Andrews, he plans to do environmental work in Africa, instead of the traditional royal career in the military.
When he started university, William hinted he would be playing a lead role in Welsh life.
On the eve of his first day, the 19-year-old said he did not want to pick an English college because he wanted a new environment.
"I also knew I would be seeing a lot of Wales in the future," he said.