Kim Jong Un Deathwatch? And his sister as possible successor?

SEOUL—As the world waits to see if North Korean leader Kim Jong Un is alive, dead, or somewhere in between at the age of 36, all eyes are turning to his little sister, 31-year-old Kim Yo Jong. She looks like the top contender to succeed him, but does she have what it takes to do that in a regime long characterized by extreme brutality?

She might well.

Kim Yo Jong’s rise within North Korea’s omnipotent Organization and Guidance Department makes her North Korea’s “No. 2” in the eyes of the Workers’ Party bureaucrats—and that makes her not only the most visible heir to Kim Jong Un’s throne but, already, a central figure of authority.

If, as some have reported, Supreme Leader Kim Jong Un is near death after a surgical procedure, Yo Jong may already have the power to fend off any challenges to her claim on leadership.