On the demise of Bhai Gurdas Singh, his younger brother Bhai Sant Singh had the honour of being the head of the Taksal. He was the younger son of Giani Surat Singh.
He learned Sri Guru Granth Sahib from his father Giani Bhai Surat Singh and elder brother Giani Bhai Gurdas Singh, including the meanings and explanations. From Bikrami 1847 onward, he would deliver his discourse on the orders (Mukh Wak) of Sri Guru Granth Sahib at Sri Harmandir Sahib. At the time of his discourse on Sri Guru Granth Sahib there used to be five Sri Guru Granth Sahibs in their perfect Parkash i.e. in the open state.
Giani Sant Singh has the honour of being the teacher of the great poet Bhai Santokh Singh and renowned poet Megh Singh. He was a great scholar, true devotee of the great God, saint and pious person. He was equally proficient in Sanskrit as well as Brij Bhasha.
At the time of delivering the religious discourse on Sri Guru Granth Sahib, he looked to be a perfect saintlyfigure. He would adorn himself with excellent and fine turban and would wear a nice chola. He bore a good moral character and was chaste out and out. The I round beard would add much more to his saintly figure.
One day Maharaja Ranjit Singh heard the discourse of Giani Bhai Sant Singh. The Maharaja wanted to test the deep meaning of the discourse or the Katha on Bhai Sant Singh himself. He sent his two servants from the Ram Bagh to bring along with them Giani Sant Singh on the request of the Maharaja. They put before the Giani the request of the Maharaja. Bhai Sahib asked them to be seated with due respect. After sometime two more servants of the Maharaja came. Giani Ji took them along with him and started to go to Darbar Sahib for his usual discourse or Katha of Sri Guru Granth Sahib. By that time the Maharaja also reached there. The Giani also took along with him the Maharaja as well. This way, the Maharaja became very happy to see that Giani Ji was determined to reach in time to the Darbar Sahib for his usual religious discourse.
Along with being the chief of the Taksal, Giani Bhai Sant Singh was the head Granthi of Sri Darbar Sahib as well. He would share the trouble and difficulties of the people. In fact, he acted like a benevolent king while doing so. He would clean the Parkarma of Sri Darbar Sahib when alone. He would pick up the droppings of the pigeons with his own hands and would pick up the fallen hair for their holy last rites. He would be in service of the Harmandir of Sri Ram Dass with his own hands. He served the Guru Ghar with such a devotion that on the day of the death of his grandson, he did not miss his usual routine and performed his usual duties in the Golden Temple. He delivered his usual religious discourse on this day also.
Once Maharaja Ranjit Singh was injured in the battle-field and fell into a ditch. ; Giani Ji lifted him up and brought the Maharaja to the fort on his back. The Maharaja did not forget this noble act of Giani Ji throughout his life. Giani Bhai Sant Singh was the tutor I of Prince Kanwar Naunihal Singh. It was with his advice that the Maharaja agreed to donate gold in service of Sri Harmandir Sahib. This service of gold was completed under the supervision of Giani Ji.
He motivated Bhai Desa Singh to donate gold for Gurdwara Baba Atal Rai. This gold adorns the two Sikh flags (Nishan Sahibs) of this Gurdwara. According to poet Megh Singh, 'this embodiment of service to the Guru Ghar and of perfect devotion to Akal Purkh (great God), Bhai Sant Singh could be compared to Beas and Janak in respect of intellect, and in respect of endurance and bravery, he could be termed as equal to Bhisham. Giani Bhai Sant Singh left for his heavenly abode on Har Sudi 8 Bikrami Samvat 1889. He left behind him the unsurpassable memories of intellectual pursuits and of service to the Golden Temple. Giani Ji was blessed with three sons, Bhai Dewa Singh, Bhai Gurmukh Singh and Bhai Jodh Singh. He was succeeded by his son Bhai Gurmukh Singh who became the head Granthi of Sri Harmandir Sahib.