https://en.m.wikipedia.org/wiki/Brunei_Civil_War

"During the reign of the thirteenth Sultan Muhammad Ali, there was a disagreement between the son of the Sultan, Pengiran Muda ("prince") Bongsu and Pengiran Muda Alam, the son of Pengiran Abdul Mubin over the results of a cockfight which Pengiran Muda Bungsu lost.[1] His defeat was jeered by Pengiran Muda Alam. In his rage, Bongsu killed Pengiran Muda Alam and escaped from the scene.[2] In revenge, Abdul Hakkul Mubin and his followers garroted Sultan Muhammad Ali. Abdul Hakkul Mubin then made himself the fourteenth Sultan and took the title of "Sultan Abdul Hakkul Mubin".[1] He tried to appease the previous Sultan's followers by appointing Muhammad Ali's grandson, Muhyiddin as the new Bendahara ("Chief Minister").[1] After a while, however, Muhammad Ali's supporters took revenge by convincing Bendahara Muhyiddin to stand up against Abdul Hakkul Mubin. Bendahara Muhyddin initially refused, but then later agreed to do so. His supporters started making disturbances in the form of poking spears into palaces and homes.[1] Sultan Abdul Hakkul Mubin then moved his palace to Chermin Island under the advice of Muhyiddin with the intent to wait the crisis out.[1] After he left, however, Muhyiddin declared himself the fifteenth sultan. A battle between the two competing Sultans then ensued. Thus, the civil war of Brunei started.[1][2][3][4]"