Superman: The World of Krypton #1

On the day that Van-L makes the passage to adulthood, riots rage in Kandor over the rights of the clones created and stored for each Kryptonian citizen in case he or she ever needs a replacement limb or organ. At the party celebrating Van-L's passage, Kan-Z confronts and kills his mother Nyra, who has removed one of her clones so that the clone might develop her own personality and become Nyra's own son's bride. This outrage sparks the Kryptonian Clone Wars.