Buy some Greenies cat treats and then try calling him by name. Reward kitty when he comes to you. It will take a bit for him to catch on but he will get it if you are consistent. I've trained all my cats with Greenies. They even do tricks
You first have to ensure that the cats are not deaf. Sit it them down in front of you and mention their names to them several times. Do this at different times for each cat. Do the same thing but this time from a distance. Do this often when speaking to your cats and with time they will be able to recognize your voice and their names.