The 'Tattvabodhini Sabha' was established by

The Tattvabodhini Sabha was established by Debendranath Tagore on October 6, 1839, in Calcutta [1]. Originally named the Tattvaranjini Sabha, it was soon renamed to Tattvabodhini Sabha with the objective of promoting a systematic study of India's past and propagating the monotheistic ideas of Raja Rammohan Roy [2]. The Sabha published the 'Tattvabodhini Patrika' in Bengali to spread a rational outlook and religious inquiry based on the Upanishads. Prominent intellectuals like Akshay Kumar Datta and Ishwar Chandra Vidyasagar were associated with the Sabha, which eventually merged with the Brahmo Samaj in 1843 to revitalize the movement [2]. While Keshab Chandra Sen joined the Brahmo Samaj later in 1857, and Dwarakanath Tagore was Debendranath's father, the founding of the Sabha in 1839 is credited solely to Debendranath Tagore [1].

Sources

1. [1] Rajiv Ahir. A Brief History of Modern India (2019 ed.). SPECTRUM. > Chapter 9: A General Survey of Socio-Cultural Reform Movements > Socio-Cultural Reform Movements and their Leaders > p. 210
2. [2] https://en.wikipedia.org/wiki/Tattwabodhini_Sabha