The man tipped to be North Korea's next leader was schooled in Switzerland where he was an ambitious pupil who enjoyed basketball and even picked up the local dialect, reports said on Monday.
Kim Jong-Un, now in his late 20s, is said to have received his early education at the private International School of Berne in the suburb of Gümligen, and then went to secondary school in Liebefeld, also just outside the capital.
When his father Kim Jong-Il nominated him as successor two years ago, media descended on the suburb to try to get a glimspe of the famous pupil.
Such was the interest the local authorities issued a press statement.
No-one named Kim Jong-Un had been on the rolls at the Liebefeld Steinhölzli school, they said, but "a young North Korean" had been a pupil from August 1998 to autumn 2000, registered as the son of an embassy employee.
"The pupil was considered well-integrated, hard working and ambitious. He played basketball in his spare time," said the Köniz commune in June 2009.
The heir apparent previously attended the International School of Berne between 1993 and 1998 under the name Chol-Pak or Pak-chol, media reports said.
A staff member told AFP on Monday that the institution was "not in a position to say anything on the subject."
The young boy is said to have learnt the local Swiss-German dialect when in Bern, renowned as difficult to master for non-natives.
"We don't know much about the third son of Kim Jong-Il," said North Korea specialist Pauline Plagnat from Geneva University.
But he is the only one who studied and is interested in politics, she said, "and was his father's preferred choice for this reason."
The academic said he was very close to his aunt Kim Kyong-Hui, the sister of his late father, and her husband Jang Song-Taek, the country's unofficial number two leader.
The foreign ministry said on Monday it was not able to comment on any links between Switzerland and Kim Jong-Un.