Ah...see, I didn't listen to the Drama CDs (or know they existed rather). But regardless of whether Lelouch knew of Arthur's connection to Euphie, I don't particularly believe he was as fond of the cat as the rest of the council. His attachment to the remaining council members is much more tangible than that toward a pet, something much more accessory no offense to pet owners.
(no subject)
no offense to pet owners.