Kim Jong-Un, the youngest son of Kim Jong-Il was born in either late-1983 or early-1984, and has been his father's heir apparent since 2009 when he was named to a position in the North Korean National Defense Commission.
Jong-Un has always held something of a favored place with his father, and they are said to be similar in many ways (both have been known to have notoriously short fuses). He's been driving cars and drinking alcohol since he was a child, and once insisted that his younger sister call him "General Comrade" rather than "brother." It is believed that he too was educated in Switzerland where he learned to speak both English and German, but much of his childhood is speculation (or hearsay) due to the secrecy of the North Korean regime.
In 2010 Jong-Un was made a Daejang (the Korean equivalent to a general), despite limited military experience. He was also made a deputy chairman of the Central Military Commission of the Workers' Party and a member of the party's central committee. All of these appointments clearly pointed to his ascendance to power when his father finally passed.
It is expected that North Korea will now enter a three year mourning period, during which time Jong-Un's power will slowly be consolidated. As he has only been in the public eye (or as "public" an eye as is possible for a North Korean leader) for a short time (unlike his father who had been groomed over a period of more than a decade) it is believed that he will share some of the ruling responsibilities with military leaders to start. At the end of the three year period Jong-Un will formally take over for his father.
It is also known that he loves the Los Angeles Lakers. So there's that too.