Like her brother, and much of the rest of their family, few details are known about Kim Yo Jong and the life she lived before reaching a prime leadership role in the North Korean government.
Here's what we know about her so far:
It was clear from a young age that Kim Yo Jong was destined for a powerful career. Kim Jong Il once bragged to foreign interlocutors in 2002 that his youngest daughter was interested in politics and eager to work in North Korea's government.
It's completely unclear where she was or what she was up to between 2000 and 2007.
In the following years, she conducted a lot of behind-the-scenes work for her father Kim Jong Il and brother Kim Jong Un. She played a particularly significant role in helping Kim Jong Un take over instead of his older brothers.
Kim Yo Jong made headlines last year after she was promoted to a top position in her brother's government: the head of the propaganda department of the Worker's Party of Korea.
That's not just a fancy title — Kim Yo Jong plays a crucial role in controlling her brother's public image.
In public, Kim Yo Jong appears to have greater freedom than other top government officials in North Korea, occasionally appearing in photographs unaccompanied rather than constantly being in the presence of Kim Jong Un.
Some have speculated that she was promoted partly in an effort to continue Kim Jong Un's dynasty. While she's out of the line of succession, some believe she could take over the country's leadership if something happens to Kim Jong Un before his kids are old enough to rule.
It wouldn't be an unprecedented role for her, either. Kim Yo Jong once briefly took control of the country's affairs while her brother was ill in 2014, according to a South Korean think tank run by North Korean defectors.
Everyone's eyes were on Kim Yo Jong at the start of the games. She shared a historic handshake with South Korean President Moon Jae In, and both broke out in smiles.
Though the two Koreas remained divided, it was a rare show of diplomacy and warmth. Given her experience in propaganda, she likely knew exactly what she was doing to try and curry favourable attention.
In April, she played a crucial role in the peace talks between the two Koreas. Leaders from the two nations met at the demilitarised zone, and Kim Yo Jong was notably the only woman at the table.
She was also front and centre during this week's Trump-Kim summit in Singapore. She played a similar role as the US Secretary of State, Mike Pompeo, standing side by side with their respective leaders during the document-signing.
Kim Yo Jong sparked curiosity at one point, when she switched out the pen that was provided for the summit with her own ballpoint pen. It's unclear why she swapped the pens, but some have speculated that it was for security reasons.
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