do you mean O Sensei's actual training partners? The one who he practiced shiho nage on as he studied under Takeda?
Good question. I guess a check of the Daito Ryu records will provide some clue as to the names of O Sensei's classmates.
I can only imagine, with both awe and terror, what it was like to have a young and very physically strong Ueshiba as a training partner. Must have been nasty..