We have 2 residents cats (female littermates) that are 2.5y old. We adopted a 9 week old female kitten 1 week ago and the resident cats are still hissing and swatting at her. Both have lunged towards her, cornered her and smacked her on the head/hiss at her. I can’t tell if they’re being aggressive or if this is still considered normal behavior. They’re both able to be in the same room but if the kitten gets too close they hiss/growl and sometimes swat. On top of everything the resident cats are now hissing at each other if they get too close. Help!