This article is from the NYPD Blue FAQ, by Dave Chapman, Alan Sepinwall and Jeff Knapp with numerous contributions by others.
Well, the fact that their last names are spelled differently
ought to be all the answer you need. No, they are not related,
though people occasionally confuse the two because of the
similar last name and the fact that both appeared on TV shows
about Vietnam at roughly the same time (Kim on "Tour of Duty"
and Dana on "China Beach").