We're after a bit of advice so I'm hoping someone will be able to help.

We've got 3 cats in the house and they all get on really really well. Sammy is the oldest at 20 months, then Pepsi and Merlin are sister/brother and are 17 months.

Recently, (Tues evening) a neighbour found a young male cat on the street (I would estimate about 9 months old) - apparently he had been hanging around for 5 or 6 days and was being 'fed' by one of the other neighbours.

However, neither they nor our next door neighbour could take him in - so they brought him to us to ask what to do and of course, my wife agreed to take him in as he really needed somewhere safe and warm and needed feeding up. We spoke about taking him to a sanctuary, but my wife is convinced that all our local ones would only keep him for 7 days then put him to sleep - and that is a definite No No for us so we agreed to keep him and try and integrate him to the fold.

A vet has given him the once over and said he was ok just under nourished. He is not chipped and has no tag and has not been neutered (we were going to have him chipped and neutered on Monday, along with getting him the jabs he needs).

We've posted on a couple of lost and found pets forums and asked along the whole street but no body wants to claim him.

On Tues night we made a bit of a fuss of him and I guess the other 3 felt a bit jealous. Wed and Thurs - we tried to reassure the other 3 - made sure they could get to their food etc. but they stayed well away from him.

The new cat, we've called him Felix - is a really nice cat, placid and loving. But the other 3 still wont stay in the same room if he is there, Pepsi (Female) won't even come into the same room if Felix is there. This morning, Sammy came into the lounge to get a drink, Felix was about 5 ft away playing with a toy and then for some reason Felix just hissed and chased him into the kitchen and had poor Sammy cornered, and poor Sammy was cowering and shaking.

Now, I know cats fight, they try to establish dominance and I know they don't always get on at first, so it all takes time. Perhaps we've been spoilt because the other 3 get on so well.

My concern is that the 3 cats' routine has been disturbed to the point where they won't even come and sit with us in the evening like they normally do, preferring instead to either go out or go upstairs to sleep on the bed. Their whole demeanour and behaviour has changed. They seem always on edge and nervous and hesitant to come for a cuddle, which is not like them at all.

Much as we have taken to Felix, I believe we owe our first duty of care to the 3 cats, and if they are being upset and put out by the new arrival then we have to address that first.

We think we may have found a sanctuary that will take Felix and will not have him put to sleep, but I am just wondering if we should give all 4 cats a bit more time to get acquainted? How long should we try it? What are the chances that they will get on? Is there anything we can do to help them get better acquainted or if there is any advice at all - then please post them. We would dearly love to keep Feilx, but not if it upsets the other 3 so much.

Sorry for the long post, but I thought it important to give the full picture.

sorry if you've said but how long has it been since you moved him in?
When I moved a new cat into my household it took 2 or 3 weeks before they would all share a room; even then it was an uneasy alliance. That said, even now, some 10 years or so later they all have their off days when they won't tolerate the presence of the others. In that respect they're just like people I think. Ironically, its the brotehr and sister that have the little spats theses days.

As long as its just a bit of hissing / chasing and no blood has been drawn I would suggest its a case of them all deciding who's top cat, which is a natural process. If "felix" has been living out and about on his own for a while he would be naturally aggressive to other cats because he would view them as competition for the food in front of him but I would expect him to calm down as he realises "hang on! I'm getting regular dinner!"
can't really say anymore than that I'm afraid.
[EDIT] its only been a couple of days.. you defo should give it more than that.

I would seperate them unless your in. Then introduce them too him one at a time. I have a multi cat house hold and i have arguments sometimes. Once he gets neutered he should be a lot better. But if he has only been around a few days i would wait until a couple of weeks before you do neuter as the owners might have been away. also a unneutered cat can wander miles from his home. If the owners are used too him doing this they might have not realised he is missing .
Also report him found too the rspca and all the vets near you too. It will cover your backs incase he is owned by anyone

We are going through this with our 12 year-old who is put out that we have a new one year-old. Time and patience is the answer. Seen so many posts on here saying the same.

Thanks for all the replies, We are going to persevere and do things gradually as has been suggested.

I'm not used to dealing with cats, I guess that's obvious - my wife says I'm worrying about nothing.

Thanks again for the words of help.

We've had this ongoing for several months. Mr Cat, very large black and white moggy, took exception to small grey tabby kitten and decided he would protest by living outdoors for a while.

He must think we humans are really dumb because needing to fill his food and drink dishes each day was a big give away that he was still around

On the coldest days they tolerate each other from across the room (small grey tabby, Harry, is quite a lot larger now ).

I laugh because when I fill their dishes they really are more concerned with food than any possible feud they may have.

Have to say that Thomas, the third cat, a neutered tom, doesn't care who he shares his home with as long as they don't eat his food or nick his place on the bed

Jarwyn - sorry to be a killjoy but I have to say it -- the problem is your other 3 cats may never get used to Felix. They may always feel pushed out by him, particularly if he is at all aggressive or tries to dominate them, or take the alpha male role.

I have never had unqualified success over the years on the occasions when I tried to bring in another cat to the equation. The best results I had were from introducing a young kitten (3 months old), as the 2 older cats semed to find this less threatening. Even so it took about 6 months before they seemed to settle down again.

Personally I feel it is a geat shame to risk upsetting the applecart. You have 3 cats who get on really well, and this in itself is fairly unusual (in my experience), and absolutely to be cherished, so in your shoes I would be loathe to do anything that might spoil the harmony.

If you have found a sanctuary that is offering a place to Felix I would take it up. After all if he is a nice friendly cat he will be adopted by someone else very soon no doubt.

My existing resident cat Bernard accepted my 2 new cats straight away (who were already bonded with each other) and that set the tone for their ongoing relationship which has got even better over time. They have the odd dispute but nothing serious and they bear no grudges.

My late cat Tabitha only ever tolerated Bernard from the moment she met him. He loved her and she sort of liked him (when she wasn't ignoring him) but I think she really would have preferred to remain my only cat. They definitely did not enjoy the relationship that my current cats have.

In my experience the nature of the relationship is set quite early on and I would be concerned about upsetting the current status quo. Some cats do need time to learn to live with each other and do go on to enjoy a harmonious life together but, as the previous poster has said, it's a shame to upset the cats you currently have if they get on so well with each other.

You probably need to give it another couple of weeks before making any decisions - but it may be better all round for Felix to be re-homed.

It took weeks before my cats would tolerate my sisters cats,unfortunately my sister died it was a so hock, me,just losing dad 3 months before her. She had two cats I bought them home with me,I only have 1bedroom flat so sis pussies were kept in bedroom,it took ages before Lil and Lucy ventured out,even now my Maddy spits and swears but the tolerate one anOther!

Cats Protection don't put healthy cats to sleep. RSPCA - depends. Some don't, some have no choice but to do so as there are so many homeless cats in the area.

Have you done any leafletting to try to find his real home?

And keep him separate at least until he is neutered. The FAB have good advice on setting in new cats:
http://www.fabcats.org/behaviour/introducing/index.php

Animals do need time to adjust to changed situations and cats are worse than most about it. Mine get upset when I re-arrange the furniture!
The whole dynamic changes when another animal is brought into the equation, and relationships between your existing cats will have to adjust. There will be a struggle for the role of 'Top Cat' for a start.
Twice I have acquired kittens of the same age from different sources hoping they would grow up pals and in both cases its been a failure and they just about tolerated one another. So it doesnt even always work introducing them young, it's more to do with personality.
You have to decide if you want things to stay the same or if you are prepared for change, because if you keep this cat, change they will.