Kim Jong-un has warned that he could start a nuclear war “at any moment” amid growing tensions with the US.
Donald Trump is reportedly considering military options to tackle the North Korean nuclear threat, and has sent an “armada” to the Sea of Japan in a show of strength.
Any decision from Kim Jong-un would likely be run past his sister Kim Yo-jong, who is a senior official in his communist government.
Who is Kim Yo-jong?
Kim was born on September 26, 1987, the second child of North Korea’s late leader Kim Jong-il and his mistress Ko Yong-hui.
Her early childhood was spent in central Pyongyang with her brothers Kim Jong-chul and half-sibling Kim Jong-un – now supreme leader of North Korea.
Her other half-brother was Kim Jong-nam, who became estranged from the family in 2001 following an incident where he was arrested in Japan after travelling on a forged passport using a Chinese alias. He was murdered in February 2017 with a deadly nerve agent at a Malaysian airport.
Kim Jong-un's sister Kim Yo-jong is a senior official in his party
Kim Yo-jong is Kim Jong-un's half sister
In 1996 Kim joined her brothers at school in Berne, Switzerland, where she studied under the name Kim Yo’ng-sun.
An employee at her school said that Kim was “overprotected” by “several women” who drove her to and from school.
The siblings lived in a private home with a residence chief, several attendants and bodyguards.
Kim’s mother regularly visited, but her father remained in Pyongyang.
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The Kim Dynasty: Inside North Korea's secretive 'first family'
Tue, February 14, 2017
The fate of the ruling Kim's family of North Korea, the world's only hereditary totalitarian Stalinist state.
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KIM JONG-SUK: North Korean founder Kim Il-sung and his first wife Kim Jong-suk gave birth to their son Kim Jong-il in 1941.
In 2000 Kim returned to North Korea to complete her education. Details of this period are scarce but it is thought that she studied at a western European university for a time following her mother’s death in 2004.
By 2007 Kim had been named a junior cadre in the communist Workers’ Party of Korea.
After her father’s stroke in 2008, she became an active force in establishing Kim Jong-un’s succession campaign.
Kim was a regular member of her father’s entourage before his death in December 2011.
Kim Yo-jong accompanied her brother on a tour of a nursing home
At his funeral she was seen leading a group of senior leaders, and stood between two party elders at the ceremony.
Since 2015 she has been in charge of North Korea’s Propaganda and Agitation Department.
She is responsible for developing her brother’s cult of personality, and according to defector Thay Yong-ho, organises all public events.
When Kim Jong-un underwent medical treatment in October 2014, it is believed that Kim Yo-jong filled in as leader.