When did Russell start the first Bible study group?

Brother Russell had the first Bible Study group in 1872 according to the "Divine Purpose" book page 187. But do we know who was "at the table"? No, because no roll call was made. But we can do some conjecture. 1) Brother Charles Russell; 2) His father J.L. Russell; 3) Conley; 4) Storrs and of course some other men. Since Russell married in 1879, his wife and mother-in-law would not have been in the room.