Kim Yo Jong’s closeness to her brother offers the prospect of fresh insight into the reclusive dictator’s thinking

During Friday’s Olympic opening ceremony, South Korea’s president greeted world leaders gathered for the Games. He also shook hands with a woman more important for her family ties than her official government post: Kim Yo Jong, the sister of North Korean leader Kim Jong Un. Ms. Kim is the first member of North Korea’s ruling family to visit the South since the Korean War in the early 1950s. Through skillful maneuvering, she has emerged as a close confidante of her older brother, serving as his emissary amid the country’s nuclear standoff with Seoul and Washington.

While the men represented potential challenges to Mr. Kim’s leadership, close observers of North Korea say Ms. Kim, who is around 30 years old, has gained her brother’s confidence by bolstering his rule. Ms. Kim is often shown with a pen and notepad, writing down comments made by Mr. Kim when he tours construction projects, shoe factories and other sites around North Korea. Ahead of one of her brother’s speeches, Ms. Kim was shown helping to prepare the text and applauding vigorously afterward. “She doesn’t try to outshine him, but rather completely supports him,” said Jung Pak, a Korea specialist at the Brookings Institution, a Washington-based think tank. Ms. Kim hadn’t been seen or mentioned in North Korean state media until she was shown at the funeral of her father, Kim Jong Il, in December 2011. Even then, there was confusion over her identity; some outsiders guessed she was Kim Jong Un’s yet-to-be-revealed wife.

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