It was in the 1662 A.D. that an important event took place in Brunei. The son of Sultan Muhammad Ali was killed by the son of Bendahara (Prime Minister) Abdul Mubin. When the Bendahara explained to the Sultan trying to justify the action of his son, he realized that justice was not in his favor that caused him and his followers killed the Sultan. Since Benhadara Abdul Mubin was a nephew of the murdered Sultan, he was crowned the new Sultan of Brunei. Upon his enthronement, Sultan Abdul Mubin chose his cousin named Pangiran Bongsu as his Bendahara (Prime Minister).
After a few years, intrigues entered into their relationship, and discontented persons started to look up to Pangiran Bongsu to lead a revolt. Because of what has appeared as a growing discontent against Sultan Abdul Mubin, Pangiran Bongsu was able to persuade Sultan Abdul Mubin to transfer his residence to Pulao Chermin, an island off Brunei, and to have it fortified. Due to the popular request of the people, Pangiran Bongsu raised the revolt in Brunei town, and soon his people enthroned him as Sultan with the regal title of Sultan Muaddin (Muhjiddin). Thus, it was how Brunei to have two Sultans reigning at the same time. The civil war ensued to have lasted for more than 10 years that caused the trade activities came to a standstill and famine visited the land. The island of Pulao Chermin which guarded the entrance to the Bay prevented supplies from getting into the town of Brunei. The island of Pulao Chermin too was denied resources from the mainland. To break this impasse, Sultan Muaddin sent a message to Sulu Sultan Salahuddin, the 10th Sultan of Sulu Sultanate and who was his cousin, asking him for aid.
The first thing the Sulu Sultan did was to go to the island of Pulao Chermin and seeked an audience with Sultan Abdul Mubin. During their meeting Sultan Salahuddin reminded Sultan Abdul Mubin that it was not proper for Muslims to fight each other. The Sulu Sultan was then allowed to go over to Brunei mainland, and to persuade the other Sultan to seek the ways of peace.
During the meeting of Sulu Sultan and Sultan Muaddin both have agreed to destroy the enemies of the Brunei Sultanate. Sultan Muaddin promised further that if the island of Pulao Chermin shall be conquered with the assistance of Sulu Sultan and his warriors, the North Borneo territory should belong to Sulu Sultan. The Sultanate of Sulu accepted this offer with delight.
Since the soldiers of the Sultan of Sulu were still fresh and strong, they carried out the war with the support of the warriors of Sultan Muaddin that totally destroyed their enemies and won the war. Sultan Muaddin then returned to Brunei mainland carrying all the captives from the island, and the Sulu Sultan returned to Sulu carrying his plunder, including the royal guns of the island Sultan. The promised of Sultan Muaddin was fulfilled by giving the piece of deerskin showing the map of North Borneo territory with the Sultan’s seal. This was done on a simple and solemn ceremony which symbolized and attesting to the fact that same territory was ceded to the Sultanate of Sulu. This document was honored since ancient time and never questioned up to the present by any authority.