What relation is Jimbo Kern to Stan Marsh on the animated TV series South Park?

Jimbo Kern was a helicopter pilot in the Vietnam War where he met his lifelong buddy, Ned Gerblanski. However, his memory of the events is heavily distorted. When he relates his memories to his nephew, Stan, and his neighborhood buddies for their history assignment, he recalls that there were amusement park rides and that he and Ned defeated the entire Viet Cong by themselves, while on horseback.

Jimbo cares for his nephew, but he gets frustrated by Stan's animal-loving nature. In the "Volcano" episode, Jimbo seemed to give up on Stan, because he refused to shoot anything on a hunting trip. All the same, at the end of the episode, when Stan shot the Scuzzlebutt, Jimbo still got upset and explained that you don't shoot just anything, especially not when it just saved your life. He then tells Stan that he'll always be his nephew, and he'll always love him, even if he is a sissy.