Behavior change in our old cat with the new cat

Question
Hi Norman.  We have a 6 year old male cat that we have had for  5 years.  His brother died last September and we have been searching for a new friend for him.  We adopted a 9 month old male cat from a friend but we are thinking we made a mistake.  Our old cat is a mellow, lovable cat who seemed content with how things were before the new cat came along.  We did expect the usual hissing and meowing from both.  However, our old cat seems withdrawn more than before and he won't lay with us to get attention as he usually does at night.  He was usually the slightly more dominant one with his brother and that is what we expected to happen with this new cat.  He did seems dominant but now he just allows the new cat to do what he wants and he just seems to sulk in the corner.  The new cat is persistant in trying to make friends but our old cat isn't having it.  We have and the new cat for over a week.  Do we need to give them more time or should this be an indication that the two are not a match.  We do have the option to send the new cat back to its previous owner if it does not work out between the two cats.  I also must mention that we did not have the space to introduce them as you have explained before in previous entries.  We allowed them to smell each other through the cat carrier and then let the new cat out of the carrier.  He  hid for a few days but then came out to explore and meet the old cat.

Answer
Laura,

Well, once the toothpaste is out of the tube, it is hard to get it back in.  So, given the situation, here is what to expect. At 9 months, the new kitty is a little over kitten age, but, in time your established cat should get along with him.

Is the new kitty fixed?  If not, that may help a good deal.

A week is not much time for them to get along after being introduced "cold turkey".  So, I believe they just need much more time.  Maybe as much as 4-6 weeks or more.

Make sure you at least try to ply your established cat with lots of treats and extra affection (if he will let you) while they begin to get along.

As long as you do not interfere and let them come to terms in their own way, they should be OK.

However, by changing the dynamics of the household, you will have to give your established cat some time to adjust and figure out how to relate to the newcomer and, also, how to relate to you!!!!!

Best regards... Norm.