Eventually , he considered resigning and joining the staff of Li Shimin 's older brother Li Jiancheng the Crown Prince -- with whom Li Shimin was then having an intense rivalry .
Du Yan apparently became a minor official in the imperial administration , but was not promoted .
Du Yan considered resigning and joining the staff of Li Shimin 's older brother Li Jiancheng the Crown Prince -- with whom Li Shimin was then having an intense rivalry .
Du Yan apparently became a minor official in the imperial administration , but was not promoted .