Mr Kim may well rely on the guidance of this powerful couple, his aunt and uncle-by-marriage, both more than 30 years his senior. Their influence became clear last week when they were photographed accompanying the late dictator on a visit to a state supermarket in Pyongyang that turned out to be his final engagement.
Mr Brown said there was a "consensus" that Mr Chang could emerge as a Regent figure, exercising significant power at least during the new leader's early period in office.
Mr Chang, 65, benefits from a significant power base on the National Defence Commission, which amounts to North Korea's supreme decision-making body. He is judged to be a pragmatist rather than an ideologue, sympathetic to modest economic reform, in line with proposals made by China.
Yet earlier in his career, Mr Chang was purged from the Central Committee and effectively consigned to the political wilderness, where he remained for three years until returning to prominence in 2007 as vice-director of the Workers' Party.
If he does try to become North Korea's de facto Regent, Mr Chang will probably face important rivals. Kim Sul-song, the 36-year-old daughter of the late leader, was close to her father and still holds an important position in the state's propaganda department.
Meanwhile, Kim Jong-nam, the former dictator's eldest son, may also seek to rebuild his influence. Originally viewed as the most likely successor, the 40-year-old fell out of favour when he tried to leave the country and make a clandestine trip to Japan in 2001.
But there are signs that he subsequently restored some of his reputation: in 2008, he called the doctors who treated the late leader after a stroke. He was occasionally allowed to speak on behalf of his father in meetings with foreign visitors.
Each of these three figures may try to be the power behind the throne. In the meantime, the official propaganda machine has sought to link the new leader with his grandfather, Kim Il-sung, the founder of North Korea who is still the country's official head of state despite having died in 1994.
The Korean Central News Agency on Tuesday hailed the young Mr Kim as a "great person born of heaven," a term previously reserved for his father and grandfather. The Workers' Party newspaper also described Mr Kim as "born of Mount Paektu", the most venerated site in the country and the supposed birthplace of his father.
The country's neighbours fear that the new leader may try to prove his mettle by provoking a sudden crisis. Both Japan and South Korea have placed their armed forces on high alert.