Heredity in North Korea and Kim Jong-Il's biography

In the official Workers Party written biography of Kim Jong-Il, it never says that he was Kim Il-Sung's son, just a loyal comrade of the socialist movement. So, like Professor Larsen mentioned, they are trying to downplay the heredity of the succession of rulers in North Korea. Just read the first couple of paragraphs. http://www.korea-dpr.com/library/103.pdf