SEOUL • The world had a close look at Ms Kim Yo Jong when she stood tearfully next to her older brother, North Korean leader Kim Jong Un, at their father's funeral in December 2011.

Since then, she has made several appearances with her brother, giggling at concerts, riding a white horse and smiling as she receives flowers on his behalf at state functions. The youthful and bubbly woman strikes a sharp contrast to the usually glum generals and ageing party cadres who follow her brother around.

Ms Kim's promotion as an alternate member of the politburo in the ruling Workers' Party of Korea, announced by state media on Sunday, is a sign that Mr Kim has absolute trust in his 28-year-old sister, who is four years younger.

It also makes her only the second woman in patriarchal North Korea to join the exclusive club after their aunt Kim Kyong Hui.

"Since she is a female, Kim Jong Un likely does not see her as a threat and a challenge to his leadership," said Mr Moon Hong Sik, a research fellow at the Institute for National Security Strategy.

Rumours have it that Ms Kim is the brains behind her brother's carefully constructed public image, according to The Guardian daily.

Ms Kim has risen to power at an unprecedented pace.

Having previously only occasionally appeared in the background, she has moved to the front and centre of media photos more recently, assisting her brother at numerous high-profile state events.

At a massive military parade in April to mark the 105th birth anniversary of founding father Kim Il Sung, she was seen rushing out from behind pillars to bring paperwork to her brother as he prepared to give an address.

In March last year, she accompanied Mr Kim to a field guidance for nuclear scientists, where he claimed successful miniaturisation of nuclear warheads.

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"Kim Yo Jong's official inclusion in the 30-strong exclusive club of North Korea's chief policymakers means her role within the regime will be expanded further," said Mr Cheong Seong Chang, a senior fellow at the Sejong Institute.

Apart from her age, little is known about Ms Kim. She was publicly identified for the first time in February 2011 when a South Korean TV station caught her at an Eric Clapton concert in Singapore with her other brother, Mr Kim Jong Chol. The three siblings, who all reportedly went to school in Switzerland, are full blood siblings, born to Mr Kim Jong Il's fourth partner.

Their estranged half-brother, Mr Kim Jong Nam, was killed with a toxic nerve agent in Kuala Lumpur in February.

In a state media photo in January 2015, Ms Kim was spotted wearing a ring on her fourth finger during a visit to a childcare centre.

South Korean intelligence officials say she might have wed a schoolmate from the prestigious Kim Il Sung University, but there has been no confirmation of her marital status or her spouse.

REUTERS