I just wondered how other peoples cats that are brothers/sisters get on? I have a female cat who loves her house and her brother who loves the outdoor life. Lottie often sits by the catflap preventing Toby coming in. If he walks past her, she often hisses at him, but if she pushes it he will turn around and attack her and she will loose the argument. She is on my lap nearly every night and he sits on me about once a month. The other night he was sat on me and Lottie came in and hissed at him and he went out. As Lottie spends a lot more time in the home, I guess she thinks shes top cat and her brother isn't welcome.