Originally Posted by Rose_P
I have had three cats at a time, and I remember when we introduced the 3rd (a male) to the 2 females who were good friends, they did not welcome him at all. They eventually lived peaceably, but the one absolute rule that they followed was that they would not share a litter pan with him. It's important to provide an extra litter pan, or maybe 3, as far apart as possible, so that the girl kitty can avoid where the boys go. I don't know why, but they seem to have rules about this and are not interested in our opinion.
My girl has her own litterpan but when the boys get downstairs, they eat her food and poop in her pan! I think they know it irritates her :-) . They know how to open the basement door and actually wait until I'm asleep to sneek down. She won't use the litterpan anymore until I dump all the litter out and put fresh in.