North Korea's Supreme Leader Kim Jong-un is, according to several sources, on the way out. There are rumours that a botched heart operation has left him in a vegetative state, and despite reassurances that he's alive and well, he hasn't made a public appearance in quite a while. There are now questions about who will take his place, should the need arise.

One of the top contenders is his sister, 32-year-old Kim Yo-jong. She has been present at top meetings with her brother including ones with Donald Trump and Chinese President Xi Jinping.

While it is thought that North Korea's top leadership is rigidly male, bloodline is also very important in deciding who rules next. Considering that, many think she will take over the reins.

The Kim family has ruled since the creation of North Korea after the second World War. Considering she has worked within the state apparatus for many years, and she is part of the family, it would be a natural transition for her to rule. 

It's also important to remember that Kim Jong-un's other relatives are either not interested in the title, or have denounced the regime completely.

Source: National Interest

Starting from a managerial position, she had quickly become a confidante to her brother in military and international matters.

Chun Yungwoo, South Korea's former envoy to international nuclear talks with North Korea, said,

When Kim Yo Jong has risen as high as she already has, she is no longer considered a woman but a leader who inherited greater legitimacy to rule than others. North Korea certainly is one of the most male chauvinistic societies in the world, but bloodline supplemented by status in the Korea Workers' Party supersedes gender.
Source: National Interest

Experts have also said that she's familiar with how things work - perpetuating a cult of personality, ruling through terror, and keeping the generals on their toes.

For now, it remains to be seen what the future of North Korea holds, if Kim Jong-un will return, or if his sister will take over, and just what kind of leader she might turn out to be.