[Mosi]

You need to take this kitten to a vet immediately. Really, right now. Find an emergency vet, or call the vet back and tell them what is happening and that you need to be squeezed in today. A kitten in this kind of condition has something seriously wrong, and kittens can go downhill very fast and not recover. If the kitten doesn't see a vet for the next 3 days he may be dead by then.

 

[Mosi]

Without being there, it's pretty hard to tell if this is play or aggression. The fact that your cats both try to get back to see each other again indicates it is play. What happens when the cats have had a tiff? do they both come back toward each other again and re-engage? Or does one go off and hide? If they come back together again right away then it is probably all in fun. If one cat is trying to get away from the other, then it is not fun for that cat, and that cat should be protected by having thier own space and having you intervene if things get out of hand.

Normally I let animals work it out themselves. but you can't have one of them or both getting hurt, and you cannot have one of them constantly annoying or chasing the other. Only you can really tell what is going on for them, by carefully observing their behavior and body language.

 

[Mosi]

No need to apologize....you are trying to do your best for the cats, and it is important to say what you feel needs to be said.

I think from what you describe that this is a case of the two of them being playful, while at the same time the older one is making sure (with the neck-scruff holds) that the kitten knows "his place", and that the older cat has seniority and is "in charge". this is normal, and is pretty much to be expected a lot of the time. The senior animal always has to make sure their place in the household is respected, and that's fair enough.

Unless someone is really acting upset by this or getting hurt I would leave them to work it out for themselves. I wouldn't even separate them when the older one is holding the kitten by the scruff. He will let go on his own, and as long as the kitten isn't being hurt it is OK for him to establish order in this way. It is like a mama cat grabbing the kitten by the scruff.