My two are 2.5 years old, brother and sister, and until recently, got on really well. Nothing substantive has changed - other than the weather and the longer days, so less outside time, but they have started attacking each other and it seems to be getting worse. They have a very large open plan kitchen diner that they spend most of their days in (when not outside), with multiple sleeping places that they seem content to take turns in. Two litter trays available, always 2 bowls of wet food. Constant supply of dry biscuits. No fighting over food or anywhere near it. Just when one is relaxing, or on me, the other will properly go for them. Seems to be the brother starting it most often. They are spayed/castrated. Both very affectionate towards me. Is this jealousy fuelled rivalry? Any suggestions? I'm not sure about investing in Felaway as they are in such a big space, I'm not sure a diffuser would make much difference?