Parker is quite a common surname, and there are several famous bearers of this name. Apart from the Parker pen which I was given by my parents as a symbolic gift when I first was packed off to boarding school at the age of 7, the one that has made the biggest impression on me was undoubtedly Charlie "Yardbird" Parker the brilliant and tragic alto saxophone player who moved jazz along by several decades as from the late 1940's. We may return to him in the future.
If we narrow the field down to the Parkers whose first name is Robert, the only one I read (and very much enjoy) is the late, regretted, Robert B. Parker, the very prolific author of crime novels, not to mention the odd western and so on. Robert B. Parker died just over a year ago and this made (still makes) me sad, although I didn't know the man. He produced over 60 novels and disciplined himself to write 5 pages every single day. His writing was (is, as it lives on!) of the classic, sometimes minimalistic US crime vein that has more than a hint of Chandler to it. But, alongside the pared-down, punchy and often funny dialogues, it also shows great sensitiviy to personal issues and Parker's characters are quite unforgettable.