I think that time is really one of the main things to help out in this situation. I've learned that you just can't make cat's like each other and some cat's just never will. But maybe you have some luck if they have gotten better over time, I wish you lots of luck! Do they like catnip? The last two cat's I had hated each other and I brought out some catnip, placed it on the floor and let them go at it. There was a little bit of growling from one of them at first but nothing got serious and eventually they started at the catnip together, I guess forgetting about the hate for a moment. We started doing this every day and things got a little better, but they still always hated each other.
