I am not too much into detective literature. Let me just give this a sloppy attempt.
Sherlock Holmes (obvious source), Inspector Hound (from Tom Stoppard's The Real Inspector Hound, Inspector Gadget (counts, right?). That would have been it if I had not recently read Verne's Around the World in Eighty Days. Since I have, I can also name Detective Fix. So that makes four. I am quite disappointed. There may be one or two more from works I have read which have eluded my mind for the moment.
How many relationships have you had?

