Hello! I've heard that males can be somewhat territorial when another male
comes into the house. My situation, we had a 5 year old female cat, and her
momma ran away, we brought a 2 month old male kitten into the house. Lucy
hissed at him for a few hours, I think just to let him know that she was
boss. He just wanted to be loved, and those two cats have been inseperable
for almost 3 years now.
I have a question, though. Did you keep the two cats separate for a little
while when you brought the new boy in? We read that it's a good idea to keep
'em separated, in two different rooms for about a week. Let them smell under
the door, so when they come face to face, it's not so much of a shock. I
guess, though, that you're beyond this stage.
Some cats will just NEVER get along, though. I would certainly watch these
two boys closely. Don't want any domestic violence incidents to get out of
hand with them...
Good luck, keep us posted!