Some analysts said his half-brother Jong Un, the current North Korean leader, may have felt threatened by his existence.
He was believed to have fallen out of favor with his father in 2001 after a widely publicized incident in which he tried to enter Japan using a fake passport, purportedly so he could visit Tokyo Disneyland with his family.
South Korea's spy agency said Mr Kim Jong Nam was poisoned by two suspected agents of North Korea. "So far, the cause of death has not been revealed, so it would be irresponsible to put forward any hypotheses".
What would the world be without another absolutely freakish story coming from North Korea?
South Korean officials confirmed on Tuesday that Kim Jong Nam died after an apparent poison attack at Kuala Lumpur International Airport. It's unclear whether the documents were genuine.
South Korean television published CCTV footage appearing to show a woman wearing a white top with the letters LOL printed on it and a mult-coloured skirt. "We are still looking for a few suspects, they are all still in Malaysia".
Even the USA government sources believe that the insecure North Korean dictator could be behind the attack.
In the past, Kim Jong-Un has allegedly executed senior advisory officials in an effort to more tightly seize power in the secretive and authoritarian state.
Ken Gause, from the CNA think tank in Washington, has studied North Korea's leadership for 30 years and said Kim Chol was a name that Kim Jong-nam had travelled under. One of them said Kim Jong-nam also had a wife and son in Beijing.
"We should take this as an action that reflects Jong Un's paranoia", Lee said. I really don't know how he (Kim Jong Un) became a dictator.
More than a decade ago, Kim Jong-Nam, the casino-loving eldest son of late North Korean leader Kim Jong Il, spoke out against his little brother Kim Jong Un inheriting power.
Estranged from his relatives, Kim was known to travel throughout Asia and frequent casinos and five-star hotels. He gasped to medical workers that he was "attacked with a chemical spray", a Malaysian official told the Associated Press. In 2011, Japanese media quoted him as saying he opposed "dynastic succession".
Kim fled to Malaysia after the execution of his uncle, Jang Song-thaek, in December 2013.
This took place despite North Korean objections about an autopsy taking place. Jong-nam's death comes two days before Kim Jong-il's birthday anniversary, which is on Thursday.
Seoul claims that Pyongyang had been planning to kill the North Korean leader's half-brother for the past five years.