Some speculate that it was his brother, North Korean dictator Kim Jong-un who may have had him killed. This would not be the first time that Kim Jong-un has had a family member killed. The most recent was the 2013 execution by anti-aircraft fire of his uncle, Jang Song-thaek, once considered the country’s second-most-powerful man, for what the North alleged was treason.
Kim Jong-nam was the eldest son of Kim Jong-il, former leader of the Democratic People’s Republic of Korea. From roughly 1994 to 2001, he was considered to be the heir apparent to his father and the next leader of North Korea.
Following a much-publicized botched attempt to secretly enter Japan using a fake passport and visit Tokyo Disneyland in May 2001, he was thought to have fallen out of favor with his father.

(File Photo) Kim Jong-il Left, Poses With His First-Born Son Kim Jong Nam.
Kim was in line for the throne: Kim Jong Nam (above right), the eldest son of Kim Jong Il. Things went bad for Kim Jong Nam when he was detained at Narita International Airport in Tokyo. The charge: traveling with a fraudulent passport. Specifically, he attempted to pass himself off as a Dominican named Pang Xiong (which translates as “Fat Bear” in Chinese). Japanese authorities, who know a fake Dominican when they see one, deported the heir apparent of North Korea to China.
Kim Jong Nam and his immediate family were attempting to visit Tokyo Disneyland.
All of this was pretty embarrassing for Kim Jong Il, who promptly canceled his own planned Chinese excursion. Kim Jong Nam quickly fell out of favor with his father, and was replaced by Kim Jong Un in the line of succession.