Two cats- one CRF, one not. Food?

This doesn't involve Zissou, but what do you feed two cats who can't eat the same food and won't stay out of each others?

Both cats are middleagey (5 or 6). Garfield is fat, otherwise healthy aside from some serious emotional problems and has had a bladder infection. Arthur is underweight, has high blood pressure, currently a bladder infection, and early CRF. He's been to the vet and is now on high blood pressure medicine and antibiotics.

So, what do you feed them? They're currently eating regular Iams dry food and 9lives wet. Yes, I know, that's probably what caused all these problems.

Is it better to feed them both CRF food even though it is likely to make Garfield even fatter and have vitamin deficiencies, or feed them both normal food? Better normal food?

And how do I convince their owner that Arthur isn't necessarily dying right this second, and it actually is worth it to do something for him?

Depends how bad the CRF is .... I used Royal canin and Max cat in senior for Kandie for about 18 months after diagnoisis ./// both are quite suitable for a adult cat"_

Of course canned is better than dry

Arthur's CRF was diagnosed only a couple weeks ago. I was trying to read the test results but it was really confusing, the vet had an emergency surgery when he got picked up. Some places it said normal, some places it said 'minor loss of function', some of the numbers from the blood test were double that of normal ones. He is still acting like himself, eating/drinking, using the box, etc.

How close are normal cat levels to normal human levels for their liver enzymes, etc?

If he is mild likely stage 1 ( caught it early ) Kandie was mid level stage 2 ...

can you read the creatine and bun >>??

INCREASE the wet of ANY kind ... the more moisture is essential with CRF ...

if he is stage one then a little LOWER protein dry ... RC and Nutro are both quality with lower protein in the seniors ... lower protein dry IS ESSENTIAL as it will tax the kidneys less