Is it ok to separate 2 brother cats?

Two of my cats are brothers, about 3 years old. We've had them both since they were very young kittens, but now we may give up one because his recurring UTI problems have gotten too much to handle. we've tried EVERYTHING.

Is this going to have a negative effect on either cat if they are separated? or are they generally adaptable?

I am sorry about the reoccurring UTI. There is no way you can keep them both?
Yes, you will probably deal with the one you kept going through Mourning. We unexpectedly lost Marbles and his sister, Snickers, has gone through a lot of mourning. Animals can mourn pretty heavily. Snickers would not eat for several days and we had to get her on appetite stimulants and such to get her to eat again. She now goes around the house and yowls horribly looking for him. It is so pitiful. Anyway, sorry I can't give you a better out look. We have just been going through this.

I had a pair of 3 year old brothers and lost one suddenly. The brother grieved for about 18 months and didn't snap out of it until we got another pair of brothers who he bonded with. And this in spite of the fact that we had other cats in the house when his brother died.

I can't recommend separating them. I understand UTI's can be frustrating, but if you have had a bond with this cat for 3 years and have trouble with it, what of the person who would adopt him who isn't bonded with him?

Yeah, the sad thing is, there are PLENTY of ways to deal with the UTI. In fact I'm not even sure he still has it, he just has a preference for urinating on the couch, and he's done it so much that the urine has penetrated the leather, foam ,and frame, and the couch is destroyed. It smells TERRIBLE and none of the cleaners make any difference, plus it's all scratched up. My wife is at her rope's end and it's either give him up or keep him locked in the laundry room except for when we're home and can keep him away from the couch.