It is known that Konohamaru is the grandson of the Third Hokage. Asuma is shown to be one of the Third Hokage's sons, but he is clearly named as Konohamaru's uncle. Are Konohamaru's parents ever shown and is their lack of appearance ever explained?
They weren't mentioned.
My guess is that they were alive and well, but just weren't important enough to be mentioned. Much like how Jiraiya's parents weren't mentioned (though Jiraiya did make a remark about them being alive, while Orochimaru's weren't).
If they had been dead, we can assume it would have affected Konohamaru's personality in the same way it affected Naruto and Sasuke.