Meet Kim Jong-un's Mysterious Sister

— -- The mysterious absence of North Korean dictator Kim Jong-un has focused attention on his younger sister who is believed to be close to Kim and in his "core circle of advisers," despite such enjoying such Western pleasures as attending an Eric Clapton concert.

Kim Yo Jong is believed to be 27 and the youngest sibling of the supreme leader, but like most of her family, details about her life are murky.

The state government has never released any official information about Kim Yo Jong, so all reports about her are based largely on stories collected by experts who have connections to the country and reading body language in public photos and videos.

Questions were raised about her rising star power in the country when she had an unusually prominent role in her father’s funeral ceremony in 2011. According to Michael Madden, a North Korean expert who runs a leadership watch blog and contributes to Johns Hopkins University’s Korean Studies site, said that she was seen interacting with senior party leaders and “pretty high level officials” during the public memorial ceremonies that were held in her father’s honor.

“She’s the only one [of the siblings] that we’ve really seen in public, having public roles,” Madden told ABC News.

Kim Yo Jong seemed to move closer the center of power after her uncle was executed and her aunt disappeared from formal photos last December.

“We've seen her lined up in the same way that her aunt used to line up with the senior officials,” Madden said.

Kim Yo Jong and Kim Jong-un are believed to be particularly close because they attended the same private school in Switzerland and, because they are close in age, they overlapped while at school.

“She lived in the embassy under an alias with her brother,” Madden said. “They were portrayed as the children of the domestics, the maid and the gardener.”

Madden does not believe she is married with children. “If she was married or had a kid, we would’ve heard something about it at this point,” he said.

Konghan Oh, a senior fellow at the Brookings Institute, said the sister has had special privileges.

“She’s been given a lot of opportunities to travel,” Oh said, telling how she was once spotted with her mother on a shopping trip to Paris shortly before her mother died of breast cancer in 2004. Yo Jung was last seen overseas in 2011 when she allegedly attended an Eric Clapton concert with her older brother, Jung-chul, in Singapore.

“This is a very unusual dynastic rule and the power is usually shared among the cousins and relatives who have shown true loyalty to the family,” Oh said. “She's inside the core circle of advisers.”

Exactly how high up she is in the country’s power chain remains a mystery, however.

Speculation about Kim Yo Jong has been heightened since her powerful brother has been absent since Sept. 3 from his almost daily appearances on North Korean media.

“Visibly he was limping some weeks before, and I think I could see some physical discomfort or pain,” said Han Park, a professor at the University of Georgia who has been unofficially involved in a number of negotiations with the North Koreans. “He might find it quite uncomfortable to walk and it may be prudent not to be seen in that physical condition.”

A key test of the leader's health or political status is expected Friday, the beginning of one of the reclusive nation’s biggest holidays, the anniversary of the ruling party.

“If he doesn’t show up, that means the extent of his discomfort is very severe, but I think chances are he reemerges because it is a very important day,” Park said.