Kim Yong Chol, a party vice chairman and former top nuclear envoy not related to the Kim dynasty, and Foreign Minister Ri Son Gwon could be tasked with handling diplomatic issues, including stalled denuclearisation talks with the United States, as they played a key role in Kim Jong Un's summits with US President Donald Trump.
Kim Jong Chol is the leader's older brother but has not been part of the country's leadership, instead leading a quiet life playing music, according to Thae Yong Ho, North Korea's former deputy ambassador in London, who defected to the South.
He is believed to be disinterested in public life and is unlikely to emerge as a major presence, though some analysts say he maintains ties with siblings and could play a more public role in a contingency.