But since his father's death and his youngest brother's elevation to supreme leader status, China has taken a very protective stance towards Kim Jong-nam, according to Japanese jouranlist Yoji Gomi, who has written a book about the exiled Kim, a man he calls a friend. Kim Jong-nam has been reported as saying that his youngest brother Kim Jong-un is nothing more than a figurehead who is unready for the leadership position he has been thrust into. Kim Jong-nam was also critical of the lavish lifestyle of the Kims and of their “military first” policy – where members of the military get dibs on North Korea's scarce resources, rather than the Communist Party's supposed policy of “people first”. As for the Chinese monitoring, Gomi suggests that Kim Jong-nam could be a “political card” for China to play if the Kim regime falls apart.
This is an interesting theory for a few reasons. According to Korean tradition, power should have gone to the eldest son, Kim Jong-nam; so skipping him in favor of the youngest son is in many ways a jarring move. Then there's the fact many North Koreans didn't even know of the existence of Kim Jong-un until last year, when he was suddenly introduced as the designated successor. By contrast, Kim Jong-il spent almost two decades by the side of his father, the founder of the North Korean state, Kim Sung-il, a move that established a clear line of succession. It is unknown how much support then Kim Jong-un actually has among the military or the ruling cadres of the Korean Worker's Party (a.k.a. the Communists), so the idea that he could be ousted as the result of an internal power struggle isn't that far-fetched.
If North Korea were to fall apart, once the period of immediate chaos subsided, it could lead to a reunification of the two Koreas. This is something China has always been wary about, and a major reason why they have but up with the craziness of the Kim regime for all of these years – China doesn't want to have Korea unified under the South, which would put an economically-strong, Western-looking country flush up against their border. So, with this in mind, protecting Kim Jong-nam makes a certain amount of sense as a “political card” to use Gomi’s term. If North Korea were to fall apart, China could offer Kim Jong-nam up as a “rightful” successor based on his first son credentials and his statements in support of the North Korean people against the excesses of the Kim regime and over-reliance on the North Korean military. He could be put forward as someone who could “restore” the idea of the People's Republic of North Korea championed by the still-revered Kim Sung-il, and could thus keep South Korea from extending their influence up to the Chinese border.