Jong-Nam is known to have been a computer enthusiast, a fluent Japanese speaker and a student in both Russia and Switzerland.
On Tuesday, after more than a decade in exile from the North, Jong-Nam -- the 45-year-old half-brother of current leader Kim Jong-Un -- was widely reported by South Korean media to have been assassinated in Malaysia.
There has been no official confirmation.
Born from his father's relationship with actress Sung Hae-rim, Jong-Nam is known to have been a computer enthusiast, a fluent Japanese speaker and a student in both Russia and Switzerland.
He lived in Pyongyang after finishing his overseas studies and was put in charge of overseeing North Korea's information technology policy.
But the chubby eldest son of the supreme leader was already seen by Seoul experts as something of a political lightweight when in 2001 he fell out of favour.
He was embarrassingly detained at a Tokyo airport, trying to enter Japan to visit Disneyland on a false Dominican Republic passport, accompanied by two women and a child.
Jong-Nam and his family afterwards lived in virtual exile in Macau, Singapore and China.
Jong-Nam's half-brother Jong-Un took over as North Korean leader when their father died in December 2011.
In an email exchange with a Japanese journalist published in 2012, Jong-Nam spoke disparagingly of Jong-Un, saying he lacked "any sense of duty or seriousness" and warned that bribery and corruption would lead to North Korea's eventual collapse.
In another exchange with the same reporter in 2012, Jong-Nam said: "Anyone with normal thinking would find it difficult to tolerate three generations of hereditary succession."
In October 2012 South Korean prosecutors said a North Korean detained as a spy had admitted involvement in a plot to stage a hit-and-run car accident in China in 2010 targeting Jong-Nam.
In 2014 Jong-Nam was reported to be in Indonesia -- sighted at an Italian restaurant run by a Japanese businessman in Jakarta -- and was said to be shuttling back and forth between Singapore, Indonesia, Malaysia and France.
In 2012 a Moscow newspaper reported that Jong-Nam was having financial problems after being cut off by the Stalinist state for doubting its succession policy.
The Argumenty i Fakty weekly said he was kicked out of a luxury hotel in Macau over a $15,000 debt.
Jong-Nam's son Kim Han-Sol studied at university in Paris. Back in 2012, when at school in Bosnia, he labelled his uncle Kim Jong-Un a "dictator" in an interview.
"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.