I just recently adopted a three month old kitten; while already having a seven year old resident cat in my home.

My seven year old cat is not a happy camper and is aggressive towards my new kitty.

I crated my new kitten to do a slow introduction, but it’s still not getting better and it’s been two weeks thus far. I’ve tried using a Feliway Diffuser, but it seems like that doesn’t work. I know I’ve waited too long to get another pet, seven years to be exact. I don’t know what to do. How do I help my older cat relax and stop hissing at my kitten? Why is my older cat so upset, hissing and tries to avoid my new kitten at times? I need serious help, please help.