I've written before about my two cats that just somehow can't really be chums. Sami is the real culprit of the unfriendliness - he's extremely jealous of any attention paid to Romeo.
A few weeks ago, they were chasing each other around the house and out into the garage - round and round they went. During the chase, Romeo's claw caught Sami's right eye. When I observed the blood dripping from his eye, I rushed him to our usual vet who in turn referred me to "Animal Eye Care Institute" in Pasadena. The doctor performed surgery immediately and told me to bring him back for a check-up in two weeks. (I might add this was all to the tune of $2,800 plus.) They released Sami to me with a collar around his neck so he couldn't rub his eyes and cause infection. Needless to say, Sami did learn a lesson - he despised the collar and paced back and forth for the full two weeks. Hopefully, the next time he wants to pick a fight with Romeo, he will remember the discomfort he felt with the collar - at least I'm hoping.