Kim was in his mid-40s. He is said to have studied at international schools in Moscow and Geneva. At one time, he was seen as the likely successor of Kim Jong Il.
In 2001, he was detained by immigration officials at Narita International Airport outside Tokyo when he tried to enter Japan on a forged passport. He was deported. He drew public attention when he said he wanted to visit Tokyo Disneyland.
Kim is known to have lived in Beijing, Macau and Singapore. He sometimes answered reporters' questions. In 2009 at an airport in Beijing, he was asked who would succeed his father. He responded that no one can answer the question for sure and only his father could decide.
He apparently did not attend his father's funeral in 2011. Observers say he did not want to interfere with the process of establishing a new regime.
Kim had not recently been seen talking to foreign reporters, but there had been sightings of him in Southeast Asia. heast Asia.