help! how can i introduce a new kitten to my kitten who i have now?

[Lala Lala]

hi, so basically i have a kitten who is now 5 1/2 months old, he is a boy and can be a bit agressive sometimes, and territorial. for example the lady who gave us him came to visit us about 2 months after we got him, and i'm guessing the scent of another cat on her angered my cat. my cat's hairs were standing up, his tail up, he looked VERY shocked and he even hissed at her!

on tuesday he is having dental surgery and is getting neutered and is staying over night at the hospital, so he'll be back home on wednesday.

getting a new kitten is a very sudden decision, and i was not planning to get another one for a couple of months. my friend got a new kitten on saturday and the guy she bought her from claimed she was 8 weeks old, i took a look at her and it was clear to me that she's only 5 weeks old maximum. the reason they're giving her to me is because they realised how much responsibility has to be taken to care of a cat, and thought that the best decision is to give her away to someone who can handle the responsibilities. and the previous owner is not taking her back.

anyway, i came home today smelling like another cat i guess, i dont know if my cat could smell it on me, coz i changed the top i was wearing around the other cat. but i think he may have noticed coz usually he purrs at me and meows. this time he didnt but he did lick my hand and wasnt aggressive towards me or anything.

can someone please give me advice on how i can manage this situtation. seeing as this will be the first time my kitten will be introduced to another kitten, i dont know exactly how he will react. i'm afraid he may attack her. my home is quite big so i can put them in seperate rooms, because i dont want my cat to come back home from hospital on wednesday to find another cat in his home. he may think he's being replaced or something.

how could i bring them two together? what should i do? how long should i wait before i bring them two together? i can definately manage to keep them seperate, but obviously eventually they'll have to meet and the 5 week old female kitten is quite small as well, so yh.

thanks a lot, and if you have any experience with this, please share it with me and how your cats behave together now. and if there are any useful websites please share them.