Choe Ryong-Hae, Vice Chairman, President
As SPA president, Mr Choe is technically head of state, although real power in North Korea is wielded by Mr Kim and his immediate family.
Analysts say his appointment suggests a generational shift in the North's leadership, especially after the collapse of the Hanoi summit with Mr Trump in February.
Born in 1950, Mr Choe is considered Mr Kim's right-hand man – frequently referred to as the regime's "virtual number two official".
https://www.thenational.ae/world/asia/north-korea-appoints-choe-ryong-hae-as-president-1.848051
Kim Yo-jong derives most of her power from her brother Kim Jong-un. The other potential successor to Kim Jong-un is his uncle, Kim Pyong-il who is Kim Jong-il's brother. He returned from overseas after a lengthy diplomatic career as ambassador in Europe, where he was essentially in exile for decades. Kim Pyong-il is Kim Il-sung's son. Thae Yong Ho, did an analysis of Kim Pyong-il yesterday in which it was reported that he is under house arrest, since his return in November 2019, because he is a preferable contender for power among the current ruling elites, led by Vice Chairman Choe, who now in their sixties, went to the same schools he did and now serve in the top party positions. KIm Pyong-il always has been regarded as a potential threat to succession, but he has remained a modest public servant with a low political profile to survive. Thae Yong Ho met him overseas in a professional capacity three times according to his interview on Channel A News Top Ten, yesterday. Kim Pyong-il served as ambassador to Poland and Czech Republic in his later assignments. Thae, a North Korean defector from the DPRK embassy in London, was elected to the South Korean National Assembly April 25 from the upper crust Gangnam district is Seoul, as a United Future Party Candidate. (Thae Yong-ho changed his name just before the election for some reason, now it's Thae Ku-min)
(Source- Channel A News Top Ten, 4.24) Kim Il Sung (left); Kim Pyong-il (center); Thae Ku-min aka Thae Yong-ho (right)
Thae's assessment is that there could be a power struggle or purge in the event of Kim's demise, while the old guard clings to the past and regards Kim Yo-jong as too young and inexperienced to rule. Thae prefers that Kim Yo-jong succeed Kim Jong-un. The program depicted Kim Yo-jong as isolated in the top echelons of power in North Korea. Even a nominal succession by her to power would be subject to resistance under the surface by the older and more experienced cadre of party elites who allegedly identify with Kim Pyong-il. The scenario presented is the classic maneuvering that takes place around the royal family before succession during the Chosun dynasty.
https://en.wikipedia.org/wiki/Kim_Pyong-il