So I need some help. I have 2 cats that I got when they were very young, been together since they were 6 months old. They were best friends, never fought, were always cuddling and playing together, grooming each other, everything! About 1.5 years ago my cat was having major stomach issues, I wasn’t allowed to go inside due to COVID. They called me saying they needed to give him anesthesia because he was trying to attack and bite everyone (mind you he has been to the same vet many times and had been the best patient and never aggressive). So they gave him anesthesia, did the tests, I brought him home. He was diagnosed with cat IBD and still is having issues to this day. Immediately when he got home he was aggressive towards my other cat and so I separated them for a little while until he had calmed down. Ever since that day 1.5 years ago he has not been the same. He is still somewhat lovable towards me (not as much as before tho), he is not as playful or happy as he used to be, and he still wants nothing to do with my other cat. They play every now and then but can barely be in the same area half of the time. I’m not sure what/if there is anything I can do. Please if anyone has any ideas or has been in a similar situation.