Luna and Kylo were brother and sister. We got them together... came home in one of those 'pet boxes/cages', (I don't know what you call them). Once here we kept the box for trips to the vet, etc. Kylo and Luna, however, didn't like that box much after they experienced freedom. Come in the same room with them carrying that box and both of them were out of there.
Skip to today. Kylo is living in that box. He hadn't been in it except for maybe twice since we got them last fall. Since Luna died Kylo seems to have taken up permanent residence in that box. We can get him out, he comes out to eat, use the litter box, and to play a little. He also likes two kittens we currently are raising for an adoption agency who will take them back once old enough to be on their own. But whereas Kylo used to nap on the cat tree.... not today, he chooses the box.
One exception.. Ashton. Kylo loves Ashton... follows him around like a pet dog would. But when Ashton isn't here, which is often, Kylo is mostly in that box. Why? We are wondering... does he smell Luna in that box? - JamesJM