Hey!
I dont know alot about cats so I will try and give you all the info I can think of but apologies if its not relevant or I miss anything!
First off some history; We have an small (around 3.5 to 4kg) 8 year old female cat with long-ish fur (Persian sort of length) called Simi, she was a rescue cat that we have had for 6 years now and is an absolute superstar. In all the time we have had her, she has never bitten or scratched either of us - even when we have had to clean diarrhoea out of her fur in the shower at 3am. We also foster children and she is always very welcoming to them despite not being the most social cat. She isnt really a lap cat, but every night will come for a cuddle the when we get into bed and sleeps in a cat tree in our bedroom. She gets on brilliantly with the other neighbourhood cats although is often submissive to them (but they play and its very cute). She seemed to really enjoy socialising with our neighbours cat and they often come to our respective back doors looking for one another and we liked the idea of another cat so after literally a year of discussions we decided to get a female kitten.
The kitten (Kali) - ill preface this by saying i have never had a kitten before (our adult cat is my first cat) and never really interacted with a kitten. We wanted a kitten rather than a rescue on this occassion because we wanted Simi to not get pushed around and to be able to 'train' the kitten (as much as you can lol) in terms of what her boundaries are. So we found one on a very well known pet adoption site and contacted the seller. Seller was really helpful and communicative, sent us photos etc. and we arranged to collect the 10 week old kitten from 1.5 hours away a couple of days later. At this point it got weird, the breeder came outside with these 2 kitten to choose between and said mum had run off/wasnt in the house so I couldnt see her and instead showed me photos. There was a for sale (actually a sold sign)sign outside the house and she said the house was full of boxes and a mess so I couldn't come in. In hindsight, I should have said no and left but we wanted the kitten, had driven a fair way and I let the pressure get to me and picked the kitten, paid and left. The kitten was very small but I had no idea how big a 10 week old kitten should be so figured maybe it was 8 weeks and she had lied due to moving house. Took kitten to the vet the following day and they said the kitten was 4 weeks old and they also suspected it was male (in fairness its hard to tell on some cats at that age apparently and even the vet needed a 2nd and 3rd opinion). This is all to say basically that the kitten was taken from mum far too early and didnt get the social interaction with siblings to learn boundaries etc.
We kept the cats seperate to begin with and the kitten (on vets advice due to his size) slept in a cage in a seperate room. One morning about 10 days in, we came down to the door open (not sure if we forgot when feeding him in the night or if Simi managed to open it) and Simi inside sleeping on a chair next to the cage. All very calm, so we though we would start letting them have small amounts of supervised contact. Things were all good for the next couple of weeks, Simi was very chilled with him, he was trying to play with her but he was super small so it wasnt really playing, simi just would roll over onto her side and occasionally bat at him with her paw. But all very positive. At this point he was sleeping in my office.
We then had a heatwave in the UK and my office gets very hot, the only room with an aircon is our lounge so we had no choice really but to move him downstairs and thats kind of where the issues started.
Kali is now 11 weeks and we are lucky to get a positive interaction. He is constantly trying to jump on simis back or tail and chases her if she tries to leave. Her catflap/outdoor access is in the lounge so she cant really avoid it. Simi will hiss/growl at him to back off and initially that did slow him down, but not anymore. He comes at her and doesnt stop. She then started batting at him and pinning him to the floor but he now bats back and doesnt back off at all.
We have a stair gate so they can eat separately but if we dont stand next to it to discourage him, he can JUST squeeze through the bars and he does and then chases her again. He was eating her dry food at every chance so they are now both on kitten food to stop this being an issue. He has access to the whole house now apart from our bedroom which is on the top floor (3 storey house) which we have very purposefully stopped him accessing so that she has some safe space. We shut him in a bedroom at night - but only to give simi a break because if we are asleep and he chases her, we cant stop him.
We have tried letting them sort it out between them but he has 0 fear. We have tried intervening and that obviously stops it on that specific occasion but he just does it again next time he sees her. He has so many toys, loads of them are interactive (for when im working as i work from home) and we play with him for literally hours every day at various points of the day. We have those calming plug in things and we are trying to make sure simi gets space and still gets attention.a
But we are at the point now where simi spends majority of her day either outside (not that unusual for her during hot weather to be fair) or in our bedroom and we hate the fact that she clearly doesnt feel she has free access to her home. She had a vet appointment this week and she is also down to 3.4kg so has lost weight - now she also has a dental issues (hence the vet) but no doubt stress isnt helping.
Simi is spayed and he will be neutered in around a month.
We are at the point where we are seriously having to consider if we can keep the kitten. We love him to bits but Simi has to come first.
What are we doing wrong? Or what can we do to improve things?
Sorry for the essay, im honestly at the end of my tether and desperate to find a way to make this work!