I have two male cats, brothers of the same litter. At meal times Percy will always go after Poseidon's food. Sometimes after he's licked his bowl clean but often before he's even finished his food. Poseidon has become very submissive, to the point that he not only willing gives up his food but even activity keeps an eye on Percy and will simply walk away ay the sign of Percy showing interest in his food. As I said, they've been together their whole life and they have separation anxiety that is very severe at eating time for some reason. They refuse to eat unless they've been served side by side and Poseidon almost seems to refuse without me their either. Oddly even Percy will barely touch his food if he's left alone in a closed room. I've tried being generous with portions and even spread out to a third feeding time instead of two. I monitor them when I can while they eat because if I step away for a minute Poseidon will leave with me and Percy will start eating his food. Is there anything I can do? Any training that has worked for others? I'll take any advice and thank you in advance.
Unfortunately, I do not think you will be able to train the cats out of this sort of dynamic. It happens because one of your cats is food motivated while the other is not. The food motivated cat is intrinsically rewarded by stealing food. Any sort of training can't really compete with that.
Besides monitoring them, which does work, even if it's a frustratingly boring and time consuming solution for you, there are a couple of things you can try, which may or may not work.
Separate them with a barrier that still allows them to see each other.
An example of such a barrier is a screen door. They will definitely be unable to bother each other, but they can still be close to each other and see each other. Perhaps that's enough to motivate both cats to eat.
Use a chip reading feeder.
As this is a common problem, people have designed feeders which are intended to only allow access to the food to the cat wearing the corresponding microchip. I'm not sure how good these things are at their job though. It might be possible that a really determined cat could butt its way in before the door to the food is able to close. It may depend on your cats' personalities whether such a machine will work.