Woman Sultan of Brunei?

What is the possibility that a woman Sultan ever existed in Brunei?

Highly likely.

In Acheh, there were four queens who ruled between 1641-1699 after the death of the famous Sultan Iskandar Muda while in Pasai, one of the earliest places which Islam was brought into Southeast Asia, had two queens in 1405-1434.

In Brunei, the Chinese recorded that,
"During Wanli Period (1573-1619), the King of Puni died without posterity, his relatives fought for the throne and there was a great war in the country... a daughter of the late king was put on the throne".

The the Sultans reigning during that time, according to the official Tersilah were:
7) Saiful Rizal (r.1533-1581)
8) Shah Brunei (r.1581-1582)
9) Md. Hassan (r.1582-1598)
10) Abdul J. Akbar (r.1598-1659)

The Queen who ruled Brunei at that time could probably be Raja Dungu, the daughter of Saiful Rizal who was thought to be a boy before its birth. Raja Dungu was married to Pg. Bendahara Pg. Mohammad and their son became the infamous Sultan Abdul Mubin, 13th in the genelogy (r.1661-1673).

During that time, it's not impossible that dynastic qurrels and feud occured because after the death of Saiful Rizal, two sons of his, ascended the throne. Knowing that Sultan Saiful Rizal had high hopes for his firstborn, but dissapointed as the son was actually a female, neverthelss, he still gave Raja Dungu large tracts of land to rule over. Being married to Pg. Mohammad, Raja of Bajau, also increase her chances to claim the throne as she and her husband would have many followers.

Despite being a woman, it is not impossible that to think that, all the Brunei court knows that her father favoured her but because she was a woman, she was "passed over" in the succesions (this is the 20th century thinking, rather than during that time, i imagine)... weather or not, Raja Dungu actually became the de-facto ruler, there need to have more research to be done on this issue before a final conclusion can be made.

On the other hand, since the Chinese records noted that the female ruler's father didnt have sons, maybe that ruler was Sultan Shah Brunei, who either abdicate or died after just about a year on the throne. Did his daughter took the throne at the people's support but not recorded when she was overthrown?

Senior members of the royal family compete for the throne. The 12th Sultan of Brunei, Sultan Mohammad Ali, was killed by Raja Dungu's son Pg. Abdul Mubin because the Sultan's son killed Pg. Abdul Son, thereafter Brunei recorded its first Civil War.

Another history note of Raja Nur Alam, the daughter of Sultan Mohd. Kanzul Alam, and sister of Raja Api as being the Queen of Brunei reigning between 1822-1824 (taken from Donald Brown, 1970).

She wanted her son, the future Sultan Omar Ali Saifuddin II, to rule after the death of her husband, Sultan Muhammad Jamalul Alam I in 1804, but this was opposed by his brother Raja Api (Muhammad Alam) who wanted to be the next Sultan. It is not difficult to imagine that maybe Raja Nur Alam prevail in her quest to make her son as Sultan because Raja Api was known to be very unpopular, without any support because of his cruel and inhumane nature. Because her son was young, she could have took over the throne, in the name of her son?...

The Brunei official history, however, recorded that Sultan Muhammad Alam a.k.a. Raja Api instead was the Sultan of Brunei, reigning between 1826-1828.