Oh, the photos are so cute, even though he does look a little bit sad.

Onyx is a chronic hairball puker, about once a week or so. I always find her black fur in it. (Why I know it's her and not the other girls.) Cats are prone to throwing up, I'm sure you knew that. Good luck with the solutions provided, hope something works for you! I've never taken action on Onyx because it only happens about once a week and she always seems fine afterwards, I think she just needed to get that ingested fur out.