[citation needed] A close paternal uncle, Maharajkumar Mani Singh was a well-known Communist Party leader who wrote Jiban Sangram.

His maternal uncle was Kumar Jyotirindra Moitra (popularly called "Botukda"), of the Sithlai family, who distinguished himself as an eminent Rabindrasangeet singer, and who later wrote the school anthem, 'Amader Patha Bhavan', for Patha Bhavan, Kolkata.

Later, Sinha completed his Ph.D. in anthropology from Northwestern University in Illinois, United States on a Fulbright Scholarship.

[6] Surajit Sinha's original contribution in Indian anthropology could be found in his articles on 'Tribe-Caste and Tribe-Peasant Continua in Central India'(1965), 'State formation and Rajput myth in Tribal Central India'(1962) and 'Bhumij-Kshatriya social movement in south Manbhum(1959) in which he viewed tribes and castes not as separate and isolated social and cultural categories but as parts of the greater Indian civilization in an evolutionary scheme under which formation of the early states in India took place.

Sinha was basically a pioneering historical anthropologist of India who combined field and archival data in a very early period of Indian anthropology.

[7][8][9] Sinha was committed to the ideologies of both Mahatma Gandhi and Rabindranath Tagore, two of the most eminent Indians in the nineteenth and the twentieth centuries.