Answer:
The most likely outcome is that Kim’s sister, Kim Yo Jong, would take over.
Step-by-step explanation:
The state deifies the Kims, and no other family member is as well positioned. Kim already had his half brother and his uncle killed. Kim has an older brother, Kim Jong Chul, but he was already passed over for the leadership by his father because, like Fredo Corleone, he was considered too weak. Finally there is Kim Jong Un’s uncle Kim Pyong Il who served as a diplomat abroad for 40 years and only recently returned to Pyongyang. He is more likely to be an adviser to Kim Yo Jong than ruler himself.