Jang, 64, is married to Kim's sister and "always believed the crown would be his [one day]", according to the source. His ambition may yet be fulfilled, since many observers believe he could take charge of North Korea as a regent while Kim's third son, the 28-year-old Kim Jong-un, gains experience.
However, Jang has recently seen his hard-line views being challenged by a group of reformists, bent on opening up the North Korean economy to Chinese-style capitalism. The source, who was approached by top North Korean officials and asked to invest in the country, added. "The government does want to open up, and the only thing stopping them from doing so is Jang."
The split in the Workers' Party, which echoes the division in the Chinese Communist party between hardliners and reformists during the 1970s and 1980s, may have prompted the recent two-week delay of the first party conference for nearly 45 years.
Meanwhile, the source said he felt that Kim Jong-un would eventually be appointed to lead the country. "North Korea does not want to be economically-dependent on China, and they want to break the umbilical cord, but Beijing has groomed Kim Jong-un, so it will be hard," he said.