Lucas, my orange tabby kitten, got adopted Saturday.

He was the last in his litter to get adopted. Except he was really close with my little sweetheart kitten, Cody. Cody came into the shelter by himself and has always been everyone's friend: dogs, cats, rats, he got along with everyone. But him and Lucas have been playing together a LOT for the past month or so. Ever since Lucas left, Cody's whole personality has changed. He is so grumpy, growling and hissing at everyone. There are 5 other kittens his age to play with, who he has always gotten along with before, but now he doesn't want them near him. He even got angry when he saw me holding another kitten and jumped into my arms and attacked the kitten I was holding. After that, he has been sticking to me, like he doesn't want me to be affectionate to any other kitten besides him (and it annoys him that it doesn't work). He does still love my dog though, its like he tries to get comfort from her. Is this behavior because he is missing Lucas?

That is the only thing I can think of. They were really close. I've fostered a lot of kittens and I've never had one react like this when another one left. I feel bad for my poor Cody, but I do NOT want to encourage his behavior. I have separated him from the other kittens for short periods of time for him to calm down. I want my little SWEETIE back!!!!!!!