Charles doesn't want to kill his son, he wants his son to live and use him to bring back dead waifu after he and VV kill the Gods.
Emperor let VV die because he tried to kill Lelouch for real. Right now, the Emperor is God but his powers are too weak.
VV had Marianne killed because she was a 'bad influence' on Charles
Turns out somebody doesn't have VV's back anymore and he's dead
Suzaku drugs Kallen
CC is Marianne's daughter and Lelouch's real sister