moved these comments here rather than have them on the page
IIXRedDragonXII: I feel this should be noted as I have just seen this happen in my NG+.
I had already saved Saint Urbain in 4-2 and he had arrived in the Nexus, but I killed him in order to force the Black Phantom that originally guards him in 4-2 to start respawning. That aside, when I did kill Urbain in the Nexus, his female follower that sits across from him attacked me as you would expect, however, his male follower that's on the opposite side did NOT attack me. I completely forgot about him, and now that I'm getting ready to finish my current game, I started Mephistopheles' quest again and she asked me to kill Saint Urbain and his followers.I of course thought it was a glitch and was ready to not be able to get my two Colorless Demon Souls, but then I remembered I never killed that male follower and sure enough, once he was dead, I was still rewarded from Mephistopheles. So, if you did what I did and Mephistopheles still asks you to kill someone who's already dead, don't panic and just see if a follower of the target is still alive.