"The Great Successor"
First Secretary of the Workers' Party of Korea
Supreme Commander of the Korean People's Army
Kim Jong Un (198?- ) is the secretive, 20-something supreme ruler of North Korea, having succeeded his father, "Dear Leader" Kim Jong Il, in December, 2011.
Almost nothing at all is known about him. Even his age is disputed, with some sources claiming he was born in 1983 and others claiming 1984. Rumor has it that he was educated in Switzerland, under an assumed name and forged identity papers. He does have a wife, Ri Sol Ju, but nobody knows who she is or when they got married.
In fact, nobody even knew Kim Jong Un existed until a Japanese sushi chef kidnapped by his father escaped back to Japan in 2001 and revealed the existence of a third son of Kim Jong Il.
Kim Jong Un first came to be seen as the successor to his father around 2010, when it became clear that his two older brothers had fallen out of favor with their father on account of being complete fuck-ups.
Then again, Kim Jong Il is rumored to have been secretly in favor of Kim Jong Un for years on account of Kim Jong Un sharing his personality "quirk" of becoming implacably enraged at the slightest provocation. Informants suggested that in Kim Jong Il's eyes, his two older sons did not have enough "fire" to rule effectively.
In any case, given how little verifiable info there is on Jong Un, you can learn pretty much all there is to know by watching this informative YouTube documentary: