Feeding multiple cat ages?

We need input. We have a 16 year old female that has a sensitive stomach, a 6 year male that is overweight (16+ lbs.), and a new male kitten. We can not seem to find the right food for all, so how do we feed individually? As we all know, cats don't tend to respect each others food dishes.

Please Help!

The only way to feed cats seperate food is to set feeding times and put them in different rooms. If you have an overweight cat, you don't want them eating kitten food for sure and if the sensitive stomach cat gets the other, you may have a mess on your hands.