But this assumption was thrown into doubt in 2001 when Kim Jong Nam was caught at Narita airport in Tokyo, trying to enter Japan with his wife and son on fake Dominican Republic passports. Since 2003, he had been living in exile in Malaysia, Singapore and Macau till his death.
Malaysian police chief Khalid Abu Bakar said in a statement that a North Korean man identified as Kim Chol who sought initial medical assistance at the KLIA2 airport customer service counter, had died en route to hospital on Monday.
The JoongAng Ilbo newspaper reported via an "unidentified government source" that the actions of the two spies attributed the attack having been authorized by the North Korean government.
"Investigation is in progress and a post-mortem examination request has been made to ascertain the cause of death", he said.
Kim Jong Un took over when Kim Jong Il died in 2011. He is believed to have been born May 10, 1971, although birthdays are always unclear for senior North Koreans, Gause said.
US government sources have also told Reuters that they believe Jong-nam was assassinated in Kuala Lumpur and blame North Korea. She was never married to Kim Jong-il.
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"My dad (Jong-Nam) was not really interested in politics", Kim told the interviewer when asked why his father was passed over for the dynastic succession in favour of his younger brother. He told the authorities they wanted to go to Tokyo Disneyland.
Kim Jong-nam - the eldest son of late leader Kim Jong-il - had voiced opposition to his father's power succession to Kim Jong-un. The major holiday this Thursday is called the "Day of the Shining Star" and will be feted with figure skating and synchronized swimming exhibitions, fireworks and mass rallies. He also had voiced disapproval of his family's control of the country.
Malaysian police said that the deceased was in possession of a passport with the name Kim Chol, according to Reuters.
Speculations as to how the half-brother, Kim Jong Nam, died have been swirling around in global media.
His death could be considered as the most high-profile death during the reign of his younger brother, Kim Jong-un, since the execution of Jang Song-thaek, the brothers' once powerful uncle, in December 2013. He was Jong-Il's eldest son, and his mother was the actress Sung Hae-Rim.
Kim was a frequent traveler to China but had not defected from the North Korean government. In 2007, Macau's Banco Delta Asia agreed to dissolve all ties with North Korea after the U.S. Treasury accused the bank of acting as the country's "willing pawn".
Cheong Seong-chang, a longtime researcher on the Kim family, said that the killing of Kim Jong Nam could happen only with the order of Kim Jong Un.