Bringing home a kitten when you already have an adult cat
On many cat sites I visit there are posts from people who decide to adopt a kitten when they already have a grown cat (10 years old in some cases). It seems that many times this causes a huge amount of stress and hostility in the current resident adult cat. It can even permanently change the adult cat's personality (cause them to hide more). The perplexed owner then asks for advise on how to get the existing cat to accept the new kitten.
Often I wonder if the owner is not being selfish. Perhaps they are just bored with the cat they have or saw a fuzzy cute kitten that they couldn't resist. They often say they want their existing cat to have a "friend" -- but the adult cat hardly thinks of the newcomer (especially a kitten) as a friend. Either way, it seems unlikely that the two will ever become buddies. Now I know there are probably exceptions but the posts are read about are from the people who need help.
Knowing how territorial cats are, do you think bringing home a kitten when you have an adult or senior kitty at home is fair? I am thinking especially of cats who have lived 10+ years without another cat around.