We inherited 2 cats, 3yrs ago. They are brother & sister from the same litter (7yrs old). They are both fixed and had their shots when I got them. Now they are fighting & hissing with each other (no claws). They are now even lunging at one another.I think it starts with the female and as soon as she sees the males she starts to hiss/growl and the male is fighting back. This goes on for a couple of days (we keep them seperated) and then they are okay for a while, playing, etc.This is the 4th time it has happened. I called the previous owner and this has never happened to her. Any suggestions...I am afraid I will come home and one will have killed the other.
Since the cats have a new home they may be stressed. This could put a strain on their relationship. I doubt that they will kill each other but they may bite and scratch each other which can land them a vet visit. If you are around when they are fighting use a water gun to help separate them. Good luck, vetcare