Kim Jong Un believed dead or dying
So, who takes over? Is there an heir in place?
Kim Jong-Il had five children, three boys and two girls. Kim Jong-Un was actually on the fourth oldest, so it was somewhat surprising he took over when his father died, although not totally unexpected as he had the highest position at the time of Jong-Il's death, and the oldest brother (Kim Jong Nam) had fallen out of favor somewhat since an incident in 2001 with a forged passport. Jong-Un had him assassinated in 2017. So there are three other children of Kim Jong Il still alive: his the brother Kim Jong Chul, the older sister Kim Sul Song, and younger sister Kim Yo Yong.
Of these it appears Kim Yo Yong appears to be hold the highest position, although with North Korea these things are always difficult to predict. Gender could come into play and I'm not sure how the NK generals view having a woman as Supreme Leader. On the other hand, she could be the only reasonable option, as it appears the older brother (Jong Chul) does not involve himself in politics much (according to a defector), but did, on the other hand, arrest his uncle in 2011 who was later killed. It may have been however, simple a rare gesture to "prove loyalty" to Jong Un