The summit between Donald Trump and Kim Jong Un will be among the most improbable diplomatic encounters in history, featuring principals who could not be more different, but who also share some surprising similarities.
Trump was the oldest US president ever to take office when he was sworn in a little over 500 days ago, and will turn 72 on Thursday.
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The North Korean leader is still in his mid-thirties and remains among the world's youngest heads of government, but has already been in power for more than six years.
The chosen heir, once his elder half-brother fell from grace, Kim was groomed for years to take his place at the top of Pyongyang's political pyramid.
And in a one-party state where according to rights groups tens of thousands languish in political prison camps, he has no need to fret about re-election or tomorrow's headlines, or to respond to them on Twitter.
In contrast, Trump reached the White House via a career in property development and reality television, followed by an unprecedentedly populist presidential campaign that upended the US political establishment.
And although he is his country's Supreme Leader, Kim does not hold the title of President. That is reserved for his grandfather, the North's founder Kim Il Sung, despite his death in 1994.
But the two leaders also share some parallels.
Both grew up in luxury, went into the family business and have appointed trusted relatives to key positions.
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Dynastic descent from Kim Il Sung is the basis for Kim's personal legitimacy -- Pyongyang's propaganda promotes the similarities between them in looks, mannerisms and even handwriting.
His sister Kim Yo Jong has emerged as one of his closest aides. She acted as his envoy to the Winter Olympics in the South, spent almost the whole of his first summit with the South's Moon Jae-in at his side, and accompanied him to China to meet President Xi Jinping.
Yo Jong is in Singapore with her brother, having flown on a separate aircraft to preserve the family bloodline in case of disaster.
Trump's father Frederick Christ Trump was a self-made property developer. The president has appointed his daughter Ivanka as an assistant and her husband Jared Kushner is a close adviser, while his son Donald Jr was part of his election campaign.
Both Kim and Trump are unbending in their demands for loyalty.
In the month starting February 28 Trump sacked or lost the services of his White House communications director Hope Hicks, chief economic adviser Gary Cohn, national security adviser HR McMaster, Secretary of State Rex Tillerson and veterans affairs secretary David Shulkin.
Kim recently appointed a new director of the military's powerful General Political Bureau described as a "highly trusted" lieutenant, and has established his authority over both the ruling Workers' Party and the military by ruthlessly purging potential rivals.
The most senior victim was his uncle and mentor Jang Song Thaek, who was executed in 2013 -- denounced by state media as "despicable human scum" and proclaimed guilty of a variety of colourful crimes and political sins.
And last year his half-brother Kim Jong Nam was brazenly assassinated in broad daylight, smeared with a deadly nerve agent as he walked through Kuala Lumpur's international airport in a hit which most analysts say could only have come from Pyongyang.
Holding hands with history
The two men share a taste for colourful rhetoric -- last year Kim called the US president a "mentally deranged US dotard" and was dubbed "little rocket man" in turn.
But in his new diplomatic role -- until March he had not left his country for more than six years -- Kim has come across as polite, respectful and even charming in meetings with the Chinese and South Korean leaders.
"The kind of counter-intuitive thing is, I think they are going to listen to each other," said Yonsei University professor John Delury. "I think they are going to get on well."
In addition to nuclear weapons, a long handshake could be high on the agenda in Singapore.
Both men have shown a predilection for grasping the palms of their fellow leaders, Trump with the likes of French President Emmanuel Macron and, more awkwardly, with British Prime Minister Theresa May.
In turn, as the cameras rolled at a farewell ceremony at the end of their first summit, Kim held hands with the South's Moon -- for several minutes.