The girlfriend and I got a new kitten; She is about half a year old. We were very careful because her roomate (they share a 2 bedroom apartment) has a 4 year old cat already. We kept the older cat in the roomate's room for a bit, while our new addition to the family explored. The three of us played with her but my girlfriend's roomate made sure to check on her cat to make sure it was all good. Also, the older cat is on weight control food so we trained him not to eat the kitten's food.
For about a week none of us noticed anything, but now the roomate's cat has started acting strangely. When she plays with the kitten her cat will just pop his head out from around the corner. When she calls him or looks at him he makes a bizarre groan and slithers back into the room. Our little sweetheart even tries to cheer him up but he won't even meet eye to eye; He will literally close his eyes and stand still or push by her. He's probably just being stuck up but what should we do with him?