He wed Sultan Omar Ali Saifuddin II's daughter, Raja Isteri (Queen Consort) Pengiran Anak Zubaidah.

Acknowledged for his sway over the royal family and populace, he worked as Omar Ali Saifuddin II's advisor during his lifetime before ascending to the throne in 1852.

[2] Abdul Momin succeeded his father-in-law Omar 'Ali Saifuddin II as sultan upon the latter's death in 1852, having previously served as regent for him during his ill health.

[7] Charles Brooke tried to persuade Abdul Momin to cede Brunei's territory from Kidurong Bay to the Baram River at the beginning of 1868, but the Sultan declined and went to the Governor of Labuan, John Pope Hennessy, for support.

Brooke thought the land dispute was insignificant and that two sovereign countries could settle their differences without the help of a third party; he later protested to the British Foreign Office, charging the Sultan of deceit and having secret plans.

[10] When this incident was brought to the attention of the British Foreign Department in April 1868 by Governor Pope-Hennessy,[11] Brooke fined Abdul Momin $4,000 for defamation.

This strategy not only forced the Sultan to comply with the terms of the lost territory but also exposed Brooke's plot to evade the yearly cession payments.

To depict Abdul Momin and his aristocracy as unfit to lead, Brooke deliberately highlighted Bruneian poverty while also quietly hinting that the Sultan need to seize control of Brunei's lands.

[7] Charles Lee Moses transferred his rights to the lease to Joseph William Torrey who sold it to Baron von Overbeck for $15,000 in January 1876.

[17] Brooke presented Abdul Momin with a plan on 9 March, asking for the ceding of areas from Kidurong Bay to Baram River in exchange for a yearly payment of $1,200.

[18] It is true that Brooke used the widespread deductions as a ploy to coerce the Sultan into ceding the lands he had been pursuing for some time, all the while avoiding making the required payments.

The treaty agreement on Brunei territory transfers and surrenders, which required Brooke to pay yearly fees for the ceded regions, was obviously violated by these acts.

On 19 December, Overbeck was appointed Maharaja of Sabah, Rajah of Gaya and Sandakan and receive control over all territory in northern Borneo after the signing of an agreement with Abdul Momin.

Peter Leys requested payment from Abdul Momin on behalf of the ship owner's family, offering 100 bundles of jungle rubber worth between $4,000 and $6,000 as reparations.

Leys appeared to be using this rejection to further his own goal of pressuring Abdul Momin to grant Brooke's request for Brunei territory extending from Kidurong Bay to the Baram River.

[27] In a meeting on 15 January, Peter Leys shared with Abdul Momin a letter from the British Government dated 2 November 1881, outlining their position on Brunei's possible territory handover to Brooke's Sarawak.

When the Sultan heard this translated position from Muhammad Kassim, the British Consulate representative, he became enraged at what he perceived as Brunei's unjust treatment.

Then, in a letter to Sultan Abdul Momin, Brooke asked for the territory from Kidurong Bay to Baram River to be turned over, saying he was willing to negotiate through his delegates.

To emphasise the need of maintaining geographical integrity for the Sultanate's sovereignty and standing within the Malay World, he compared Brunei to a body that had lost its arms.

Even when the Sultan first refused, Brooke persisted in pressuring Abdul Momin to yield territory from Kidurong Bay to the Baram River.

Due to worries about economic disruption and Labuan's trading reputation, British consuls like as Pope-Hennesy and Bulwer originally supported Abdul Momin against Brooke's expansionist intentions in Brunei.

But over time, British support for Brooke was progressively altered by his tenacious strategies, which included influencing events like the Baram River conflicts and withholding payments.

[7] Realising that Brunei would become extinct, Abdul Momin declared the Amanat,[33] an oath between the Sultan, Wazirs, Manteris, and holders of Tulin rights not to cede or lease any remaining territories to the foreign powers.

[34][35] The Sultan met with his fellow nobility in 1885 in an effort to secure the kingdom's existence, and the two of them issued a proclamation promising not to give over, lease, or otherwise release any additional territory to foreign forces.

In addition, the Amanat upheld the value of individual property rights and emphasized the significance of land and slave inheritance in line with long-standing Bruneian practices.

This flaw is emphasised since the Amanat's failure to work was a major factor in Trusan's downfall and served as the impetus for the Brookes family's claim to Limbang.

The ceremonial spear, sword, and crown were among the other regalia that were delivered to Hashim during a dinner that was held forty days later to commemorate the conclusion of the mourning period.