I had two cats. One was quite old (13) and one is young (4). Last Thursday the older cat passed away. Since that time, the younger cat has developed an eating problem, being sick, meowing oddly and also acting oddly. Can it be possible that the younger cat is just missing the older cat and we should just get him a friend as quickly as we can? Or do u think there is something wrong?
First, I am very sorry for your loss of your older cat.
It is certainly possible that your younger cat is mourning the loss as well. However, the meowing, change in eating behavior, and "being sick" you are describing could also be medical. It shouldn't be assumed that he is just grieving until any medical causes are ruled out. I would recommend bringing him for a visit to your veterinarian.
Getting a kitten right away is probably not the best thing for you or your cat. Once some time has passed, however, it is my belief that having 2 cats is always better than just one. I would recommend that you make sure your kitty is healthy first, give him (and yourself) some time to adjust to being without your older cat, and then consider adding to your family.
Also, I am not sure what caused your older cat's death. If it was something contagious or the cause is unknown, that would be another reason to bring your younger cat to a veterinarian soon and to wait before introducing another cat into the household.