Hi Bluebelle. Who were the "others" that were playing Bluegrass music before the Monroe line-up I mentioned? That would sure be news to me. Lots of old time string bands of course, but the only ones who even come close to a Bluegrass form were the Morris Brothers. Snuffy Jenkins and Pappy sherril used the three finger banjo and fiddle, but they sure didn't "sing" in a bluegrass style. That's Monroe, for sure.
These kind of discussions are lots of fun (if you care about such stuff) and sometimes there are great arguments, with everyone bringing in their evidence. Same as if someone asked "who invented Rock and Roll"? Some would say Joe Turner, some, Jackie Brenston (Rocket 88) and the odd person would say "Elvis". Of course Presley popularized it, but there were many playing EXACTLY that form of music before (all black). Nobody that I ever heard was playing "Bluegrass" before Monroe.