SEOUL—The Winter Olympics of 2018 were Kim Yo Jong's international coming out party. The world’s press gushed about the younger sister of North Korean Supreme Leader Kim Jong Un. The debutante—slender, smiling, gracious—seemed to be so very different from her porcine brother. But now that his health is in question, and amid conflicting reports that he could be at death’s door, his little sister may well be first in line to carry on the family dynasty.

“ While she may not be overly qualified to rule, she has this: she survived her brother’s bloody family purges. ”

Sister and brother have been close for years. She has advised on key events in the North Korean capital of Pyongyang, encouraging construction of modern apartments, ski slopes, even an amusement park, but it was during those Olympics that she shone as a major figure before the world. It was then, at a luncheon meeting in the Blue House, the center of power in South Korea, that she gracefully handed the South’s President Moon Jae-in a handwritten note from her brother suggesting they get together for a summit.

As a Blue House spokesman described the encounter, Kim Yo Jong embellished the written verbiage with polite words of her own. Big brother hoped they could get together sooner rather than later, at the “earliest convenience,” she said. Moon, who had been looking for reconciliation with the North, was thrilled. “Let’s create the environment for that to happen,” was his all-too-eager response.

Ah, those were the days. Now, after all those summits between Moon and Kim—and between U.S. President Donald Trump and Kim—the atmosphere has cooled again while both Koreas struggle through the coronavirus pandemic that may also have caught Kim in its feverish grip. More than ever, Yo Jong is looking like Jong Un’s most obvious heir apparent, and while she may not be overly qualified to rule, she has this: she survived her brother’s bloody family purges.

Kim Yo Jong is young—she’s 31— but she’s older than her brother was when he inherited absolute power from their father in December 2011, just shy of his 28th birthday. And Yo Jong is a familiar face to North Koreans. Big brother has been promoting her as a visible number two for years now. If Jong Un succumbs to the kind of cardiovascular issues that are inevitable for one who’s 5’7”, tips the scales at 300 pounds according to South Korean intelligence, is a chain smoker, drinks heavily, and works hard, few other contenders have his little sister’s high profile.

Previous contenders for the throne, or would-be powers behind it, have not fared well. Jang Song Thaek, his father’s sister’s husband, had an inside track on power during the later days of Kim Jong Il’s rule. After Jong Il died, Jang was fully expected to advise young Jong Un on the ways and wiles of governance. But less than two years after Kim Jong Un took power, he had Uncle Jang charged with corruption and power-grabbing, beaten, dragged before a judge, and executed. Kim also had his older half brother, who’d been living a playboyish life in Macao, snuffed with VX nerve agent in 2017.

Bruce Bennett, who follows Korea for the Rand Corporation, believes Kim may want his sister to keep the seat of power warm for when his son is ready to take charge. But the boy was born in 2010, date uncertain, so Kim Yo Jong’s regency would be pretty long. Kim may believe his sister is a safer bet as successor-in-waiting because in his view she “would not be able to take over the government herself,” says Bennett, unlike the highly qualified, deceased, Jang Song Thaek.

Kim Yo Jong was named an alternate member of the politburo at her brother’s last publicized appearance on April 12. She rose to that position after having been authorized to make public statements in her own name criticizing South Korea for bowing to Washington’s wishes about demands for an end to the North’s nuclear and missile program.

As quoted in the North Korean state media, this lissome young woman could be a tough cookie—not exactly the charmer she had appeared when she and Moon met during the Olympics.

When South Korea leveled official criticism at the North’s recent missile tests, Yo Jong fired back, "The South side is … fond of joint military exercises and it is preoccupied with all the disgusting acts like purchasing ultra-modern military hardware.” She did not mention South Korea’s President Moon Jae-in by name but called the Blue House, the center of presidential power, “a mere child”—like “a child dreading fire” whose behavior was “so perfectly foolish.”

"They meant they need to get militarily prepared but we should be discouraged from military exercises,” she declared in a flight of verbiage worthy of the North’s best rhetoricians. “Such a gangster-like assertion can never be expected from those with normal way of thinking."

It would have been impossible for Kim Yo Jong to utter such caustic words had Kim not wanted to push her into the spotlight and move her up the hierarchy. Among her official positions Kim Yo Jong has served as vice director of the propaganda and agitation department of the Workers’ Party and was elected last year to the Supreme People’s Assembly, the North’s rubber stamp parliament.

All that background may not qualify her in a male-dominated society, but she does carry on the sacrosanct “Paektu line.” That’s the blood relationship to her grandfather, Kim Il Sung, who was installed by the Soviet Union as North Korea’s first leader after World War II and ruled for nearly 50 years, and to her father, Kim Jong Il, mythologized by North Korea as born in a cabin on sacred Mount Paektu, the Korean peninsula’s highest peak and a former hideout for guerrillas battling Japanese colonial rule.

“The logical successor will be Kim Yo Jong,” says Evans Revere, a long-time diplomat dealing with North Korea at the U.S. embassy in Seoul and the State Department. “She is a member of the Kim family. Clearly, she is being groomed for greater responsibilities, as evidenced by her recent promotions, her elevated public profile, and her self-confident, almost cocky, comments.”

Bruce Klingner, northeast Asia expert at the Heritage Foundation, observes “the usual assessment would be that a ‘Confucian Korean culture’ would never choose a woman” but “Kim Yo Jong has gained prominence.” Kim Jong Un “may have designated her since she is likely the only person he trusts. If she were chosen, the regime would emphasize the continuity of the Paektu bloodline.”

Others, however, doubt the elite surrounding Kim would be in a mood to accept her except, perhaps, as a figurehead.

“I doubt she could consolidate power like her brother and father did,” says Dan Pinkston, long-time North Korea analyst, now a professor at Troy University here. “Maybe she could be part of collective leadership, but I don't think it would be sustainable.”

If Kim “is seriously sick or dies tomorrow,” says Choi Jin-wook, a North Korea expert and former director at the Korea Institute of National Unification, “leadership would go almost automatically to Choi Young Hae, deputy chairman of the state council.” Kim Yo Jong may be “a legitimate successor and Kim Il Sung’s granddaughter, but she is not quite ready for the supreme power.”

More likely, Choi predicts, “there will be a power vacuum and some instability.” It’s exactly that possibility, however, that suggests that Kim Yo Jong may be the one to rise above quarreling factions in the armed forces and the party.

Bruce Bechtol, author of numerous books and papers on North Korea’s leadership, puts it this way: “Her power base will be even weaker than KJU when he first started. Plus, there has been no preparation for this move. That said, if he dies, there may be no other alternative.” Yes, Kim has an older brother, Kim Jong Chul, 38, born to the same mother, but he’s “known to be gay and has no support in the party or the army.”

Then too, says Bruce Bennett, “ I have also heard that the senior North Korean elites are done with the Kim family. “ Disillusioned by Kim Jong Un’s failure to accomplish “many things he has attempted, like sanctions relief,” says Bennett, they may be happy to let the remaining Kims “die of COVID-19 as the cover story to allow someone else to take leadership in North Korea.”

Whatever happens, there’s no doubt that Kim Jong Un’s lifestyle is catching up with him. If he’s not in “grave danger,” as one report put it, he may still be seriously ill. At 36, “Kim is grossly overweight and likely suffers from a number of serious chronic health issues, including cardiovascular problems,” says retired U.S. diplomat David Straub. “These problems are exacerbated by the enormous stress he is constantly under as the leader of a rogue state and under constant threat from within his own state as well.”

All of which means that little sister, her big brother’s understudy, may be rehearsing for center stage. “It's hard to imagine a woman being the real leader of a regime as macho as North Korea’s,” says Straub, “but it’s conceivable that top male power players there might, in a pinch, agree on installing her as the symbolic leader."

If some of her public remarks are any clue, however, she may reject the symbolism and prove to be every bit as ruthless as her megalomaniacal brother.