Shin Kun was a male Jaffa and the former First Prime of Yu-huang Shang Ti. He had served his God since he was a toddler. For much of his life, any thought of disloyalty to his lord was inconceivable to Shin Kun. But as Yu's physical and mental health continued deteriorating, Shin Kun was forced to face the realization that his God and Lord may be powerful, but is neither omniscient nor perfect.
He had to cover for Yu's slips of memory and mood swings more and more often as time went on, straining his ability to create the appearance that all is well. To this end, he enlisted Yu's faithful body servant, adviser and several important scholars in an attempt to hide the slow but steady decline in Yu's ability to act as their ruler.
Born in Yu's court to a woman Yu later took as a concubine, Shin's unfailing loyalty and skill helped his master to increase his power among the other System Lords significantly over the past three decades. Unmarried and with no living family, he had devoted himself to military matters and to improving his skills as a soldier and guardian. (SG1: "Living Gods: Stargate System Lords", "Four Dragons")