The middle initials threw me off. Maybe if I'd just concentrated on "DR" and "BK" (or just took a quick peek at the UNIX article on Wikipedia) I might have got it...
Ken Thompson is also the one I am most familiar with and most in awe of, of this group, so that's why I could readily recognize his initials.
I am surprised though you did not recognize DMR (Dennis M. Ritchie) and BWK (Brian W. Kerighan). :-)