How can I integrate my cats with a new kitten?

We adopted a kitten who is 5 months old a few days ago. He is coming into a household that already has 2 cats that are brothers that we have been raising since they were six weeks old (They are now 2yrs old). We tried to follow instructions from our cat book and separated the older cats from the kitten so that they could slowly get used to his smell. But the kitten wanted nothing more than to play with the cats and escaped from the room he was in. Now, the 2 adult cats are on edge and upset. One of our cats used to be so sweet and loving and now is too worried about the kitten to care about us or to even want to go near anyone. He has pretty much secluded himself from everyone else. The kitten is continuously going up to each cat and sometimes with one he will get a lukewarm response, but with one he will get hissed at and swiped at no matter what. But he doesn't seem to care and still wants to play. Is there any steps that can be taken to get these cats to get along? Sometimes I see the adults hissing at each other now for no reason and I have never seen that with them before. I want the kitten to fit in but I cannot do it at the expense of my older cats. I need some help please!!!!!!!!!