I got a kitten on monday. I already had two adults cats at my house. The one cat is fine with the new kitten they get along,now my other cat hisses and growls at my kitten and makes the kitten scared. Ive tried to put them in the same room for a little bit but my adult cat gets very very upset and like i said before hisses and growls. Im afraid my adult cats going to either get violent with the kitten and hurt it or it's going to resent me for getting a new cat. What can i do to get them to feel comfortable with each other?