Sorry this will be sort of long probably. We've had cats my whole life. When I was a kid, we lived in the country on a farm. We had barn cats, house cats...they all just coexisted, I don't remember having to do introductions or any big issues. As an adult, My husband and I got a cat when our oldest daughter was about a year. She lived almost 21 years. When she was about 14, we took in three 1 day old bottle babies to foster. We ended up keeping all three siblings and we adored them all. We lost one at 10 to cancer, another at 12 from a saddle thrombosis and then just over a year ago, I lost our last one, just a few months shy of her 16th birthday. I was devastated and swore I wouldn't get another cat, not for a good long while anyway. My daughter who was almost 16 too, had never known life without a cat, the kittens were only a few months old when she was born. We lost our girl in September....by December she was really, really missing a kitty friend. So she started volunteering at the humane society and got her cat fix that way. About three weeks into that, she started talking about a kitty that was a little older, that nobody had enquired about and he'd been there several months, looked sad...etc. So I went with her to meet him and he was so sad and sweet. He'd been an outdoor neighborhood stray until someone had brought him in. We brought him home to foster and a ended up adopting him a few days before Christmas. He's probably at least 8 years old, maybe a little older, he was definitely not used to being in a home, but he did great, he didn't like to be picked up or held, but he loved to have his neck scratched and a few rubs down his back, but he doesn't like to be overstimulated. He took to home really well, he has spots around the house that he made his own and he follows us around. He is really a sweet, unique old fella...a little on the grumpy side, but we just knew his boundaries. So my daughter continued to volunteer occasionally and an opportunity to foster a couple almost 5 month old kittens came and we decided to do it. For the first several weeks they were here, our resident cat didn't even know they were here. They were down in the bathroom off the back room and he never went back there. One afternoon one of the kittens escaped and ran right up to our resident cat, there was some hissing on his part and we got the kitten and put it back. It happened another time when we had company and someone didn't get the door shut and they both escaped and we didn't know. They weren't out too long, we got them put back and after that he was curious. At the shelter he seemed to ignore the other cats so we started talking about keeping them, we were in love at that point. One of the kittens was super lovey and the other very skittish of humans having been born in the shelter. But they were VERY bonded. We hated the idea of them being separated after we had raised siblings, we knew how they loved each other. The both kittens had become very attached to me and I adore them both. We didn't really follow any kind of plan. We moved the kittens to a room in the main part of the house for a few weeks and they all heard each other through the door. We would shut resident cat in a room and let the kittens run the house for a bit every day and put a gate in the door so they could see each other then eventually let them out together for little bits of time. We have feliway optimums plug ins going and I have no idea of they help or not. It seemed to be going okay...with some hissing and growling from resident cat, but felt that was fairly normal. They were able to be out together for longer periods of time and seemed to be doing well. We went ahead and paid the adoption fee and felt pretty good about it. They eat in their room and resident cat eats in his room. Before they came he loved to lie on his corner of the table in the dining room where I do puzzles. He also had a cat tree that he would sleep on by the window downstairs. Since they have had more run of the house, he barely comes down and if he does, he doesn't relax in his places. The last few days he's become even more grumpy, swiping at us if we try to pet him if the kittens are around, hissing at them more and before if he hissed or swatted at them, they'd back off and run away, and the female still does. She has learned to just leave him be for the most part, but our male kitten is fascinated by him. He follows him around a little...and he does this army crawl thing where he drags himself over to him and sometimes rolls his belly up to him. The last day or so though, if resident cat hisses or swats at him, our male kitten has growled back and swatted back. So we have put them back in their room for a few days for a cooling off period. While they were locked up, resident cat came down and was all over the house, in his spots some and seemed a little happier. Today we let them back out and things went really well...until this evening when the kittens got up on the puzzle table and went to sleep while I was working. When resident cat came down and jumped up there he started sniffing at the male kitten who was asleep, then he woke up and growled a little at our old guy which caused him to get made, hiss and then run off back upstairs. So at meal time, we locked the babies back up and they will probably stay in here most of the day tomorrow while I'm at work. They tolerate being around each other most of the time, and were doing so good. I felt pretty good about it. Now I'm just really worried that we made a huge mistake. We love the babies and won't give them up at this point, but we will have to find a way to make resident cat happy again. It literally breaks my heart...he he was such a happy old guy to have his home and all his places and his people...and I feel like we just ruined his life. We love him so much, we just wanted him to have a happy home after al his years on the streets and obviously, just because he ignored cats in the shelter didn't mean he doesn't care. We adore him so much. And as much as I love these babies, and love the cuddles from our little guy, I do wish at times I'd said no to fostering and just left resident kitty as the only one. I don't know if he'll ever be happy again at this point.