Spraying him because he's talking sounds really mean to me. Some cats like to talk more than others. From your siggie I think one of your cats is a Siamese? These cats are very talkative, social guys. Please do some reading on this breed, they do other things you may consider "annoying". They are very intelligent cats.
My Ginza is only part unknown Oriental cat and he talks sometimes, very loudly. He's also the one who opens doors and cabinets, and flushes the toilet. My Pixie, general mixed cat, is a talker, my husband even has entire conversations with her. She likes to talk about her day, or tell us she's BORED, or tell us to play with her, or tell us she's hungry. Yes, we can tell from the tone of the meow which it is.
Since you've already taken him to the vet, and he's got a clean bill of health, then he's just a talker. There are nicer ways to train him to not chat so much. I've never tried them, so I can't vouch for their effectiveness. The two I remember:
1. Ignore him when he talks. Eventually he won't talk so much.
2. Have a loud noise, i.e. coins in a can, a big jangle of keys, and throw them down on the floor to make a loud sound everytime he starts talking. Reward any silences with a treat.
Others may have better suggestions. I've never tried hushing my cats, and actually think it's adorable when they're talking.
EDIT: OK, I just saw in your pics that Roxy is the Siamese, and the "him" is the black cat. Your description of him as part unknown Oriental could be right, then.