The noble Peacock family were the rulers of Gongmen City, and may have been for generations. As explained by Soothsayer in the opening narration, the peacocks brought joy and prosperity to the city through the creation of fireworks.
However, Lord and Lady Peacock's son, Lord Shen, developed a disturbing interest in the power of the powder used in the fireworks, and began experimenting with the powder's destructive potential. Concerned, Shen's parents turned to the Soothsayer to know what his future held. She fortold that Shen would be defeated by a Warrior of Black and White. This prophecy was overheard by Shen, and he quickly set out with his warriors. Filled with horror upon seeing his son return after having massacred a farm village of pandas, the Peacock king banished Shen forever for his crimes.
Presumably soon after the banishment, the noble Peacocks died of broken hearts from losing their son, and the throne was passed on to the Master's Council.
Decades later, Shen perfected his weapon and returned to the city, reclaiming his throne after defeating the Master's Council. With his new power, Shen set his plans for world conquest in motion, having dozens of cannons manufactured within his family's fireworks factory. Upon Shen's death at the hands of the Dragon Warrior, the peacock family line came to an end.