Introducing new kittens

My partner and I brought a new kitten 1 month ago, he's 4 months old called Cooper is very playful and cuddley. We both work full time and the vets suggested getting a second kitten so Cooper has a bit of company so on Friday we got Mimi a 3 month old kitten.

Now we looked up some tips online and our house isn't particularly huge so keeping them in separate rooms for weeks would be massively difficult, it's also very difficult for us to spread our time across both of them when they are in separate rooms without them calling out for attention.

We found some probably bad advice online that said to keep things calm and just let them meet, ignore the hissing and growling and just make sure they aren't fighting. Well things have gone a bit wrong, Mimi seems to really like Cooper she'll follow him everywhere. Cooper hates Mimi and hisses at her, he's never attacked her bar the odd jab (without claws) but also Cooper has stopped eating except for a few treats, he won't come near us if Mimi is around either and I'm not to sure what to do, we tried to go back to separating them and trying to transfer there scents on each other but Cooper just hissed at us and runs into a different room. The closest we got was putting some treats down next to Mimi while she was sleeping and he ate them, realised she was there and started hissing again. Mimi seems pretty unaffected by all this.

Any ideas for us? Should we change tactics or should we just carry in introducing them as we are and hope they get along?

Cooper is too stressed to eat, he is very stressed and needs a place of his own to start to feel confident in your home so yes, you will need to separate them. Try warming up his food to release the aromas or crumbling a little bit of treat on his food. You need to make sure that he eats something. Cats can develop fatty liver if they fast for periods of time.

I used a feliway difuser, it releases fake friendly cat pheromones which can help relieve stress. 

Here's a guide to introducing cats:

And another with some great tips.

The situation isn't as bad as you think. Mimi already likes Cooper and Cooper just has to build his confidence up to a point where he can leave his scent everywhere and not feel so intimidated. He will be fine in his separate room for awhile, this process shouldn't take weeks.