Bhai Desu Singh, (d. 1781), was the second of the five sons of Kaithal Kingdom ruler Bhai Gurbaksh Singh of the well known Bhai family, deriving its name from the celebrated Bhai Bhagatu, contemporary of three successor Gurus, Guru Arjan, Guru Hargobind and Guru Har Rai. According to Bhai Santokh Singh, Garb Ganjani Tika, Desu Singh was the fifth in the line of Bhai Bhagatu`s descendants. His father, Bhai Gurbaksh Singh, was a close associate of Ala Singh of Patiala and had carved for himself some territories around Sirhind and Kaithal besides his ancestral possessions in several villages around Bhuchcho, near Bathinda.
After his death in 1764, his territories were divided among his sons. Desu Singh collected a force, and, advancing from Bhuchcho, marched straight to Kaithal and defeating Bhikh Bakhsh and Niamat Khan. two brothers in possession of Kaithal, established himself there as an independent chief sometime between 1764 and 1768. He began further to extend his territories and seized the town of Thanesar with one of its two forts.
This excited the jealousy of another Sikh Jat chief, Mit Singh, who seized the second fort at Thanesar, and after his death, his son, Bhariga Singh, evicted Desu Singh`s forces from that town. Bhai Desu Singh also fell out with Raja Amar Singh, of Patiala, in 1778, because he did not support the Raja in his punitive action against Hari Singh of Sialba, who had been friendly with the Kaithal chief. After dealing with the Sialba chief, Raja Amar Singh sent a force against Kaithal, too, but an attack was averted by the intercession of some of the Bhai brothers. Bhai Desu Singh died at Kaithal in 1781.
- Griffin, Lepel, The Rajas of the Punjab [Reprint]. Patiala, 1970
- Gupta, Hari Ram, History of the Sikhs, vol. II. Delhi, 1978
- Santokh Singh, Bhai, Garb Ganjani Tika. Lahore, 1910
- The Sikh Encyclopedia