Kim Yo-Jong is vice department director of the Central Committee of the Worker's Party of Korea -- and little sister to North Korean leader Kim Jong-Un, which makes her the most powerful woman in the nuclear-armed state's poltical hierarchy

Seoul (AFP) - With her elevation to North Korea’s powerful politburo, leader Kim Jong-Un’s little sister – and chief image-maker – has established herself as the most powerful woman in the nuclear-armed state’s political hierarchy.

Kim Yo-Jong’s promotion to membership of the North’s top decision-making body underlines, analysts say, the level of trust her brother places in one of his closest aides and confidantes.

Ruling North Korea has always been a family business, but one where the substantial personal benefits on offer are matched by the potential for a catastrophic – and sometimes fatal – fall from grace.

Kim Jong-Un’s half-brother, Jong-Nam died in agony at a Malaysian airport earlier this year, poisoned by nerve agent-wielding assassins in a hit that North Korea watchers say must have been given the nod by the leader himself.

Yo-Jong is believed to be in her late 20s, making her the youngest member of the reshuffled Workers’ Party politburo that was unveiled at the weekend.

She is the only one of Kim Jong-Un’s siblings to hold an official title and – in a family tree complicated by their father Kim Jong-Il’s various marriages and partnerships – enjoys a special relationship with her brother in that they also share the same mother.

“They share a life-long bond and her promotion to the politburo means Kim Jong-Un has complete trust in her,” said Professor Yang Moo-Jin of the University of North Korean Studies in Seoul.

“She could be the one to take over from Kim in the event of his absence,” Yang told AFP.

Like her brother, Yo-Jong was partly educated in Switzerland and her first explicit appearance in North Korea’s state media came in 2009 when she accompanied her father on a visit to an agricultural university.

She became a regular member of Kim Jong-Il’s entourage until his death in 2011 and featured prominently in official photos of the funeral, mourning alongside her brother.

Graphic on North Korea's ruling dynasty.

After Kim Jong-Un took over the leadership, her public career in the party propaganda department progressed in leaps and bounds and, in 2014, she was listed as a “vice department director” in the party’s central committee.

According to Michael Madden, editor of the North Korea Leadership Watch website, her official propaganda role made her “the leading image maker for her brother and (North Korea) as a whole.”

With the exception of Kim Jong-Un’s wife, Ri Sol-Ju, Yo-Jong is the only relative with whom the supreme leader is known to have a close relationship.

External recognition of her position and influence came earlier this year when she was named among seven North Korean officials targeted with US sanctions for “ongoing and serious human rights abuses and censorship activities.”

Cheong Seong-Chang a senior researcher at the Sejong Institute think-tank in Seoul said her promotion to the politburo presaged a more visible presence at the top of the top of the political hierarchy.

“She is expected to play increasingly greater roles down the road,” Cheong said.

North Korea watchers have long speculated that Yo-Jong was being groomed to play the same leadership supporting role as her once powerful aunt, Kim Kyong-Hui.

Kyong-Hui was a close aide to her own brother and late leader Kim Jong-Il for decades, assuming senior positions in the party and becoming a four-star general in 2010.

But she largely disappeared from public view after her husband Jang Song-Thaek was executed in 2013 for charges including treason.

She and Jang had been seen as the ultimate Pyongyang power couple, and instrumental in smoothing Kim Jong-Un’s transition to power, before Jang fell from grace.