how to introduce new cats to an old one?

Hi
I have a male tabby called Mac who has been with us for 16 years. He's pretty much ruled the roost the whole of that time.  Now a friend is emigrating and is looking to rehome his two male cats who are 7 years old and brothers. They are a very loving pair but my own tabby is infamous for being grumpy and only friendly on his terms.  I've said we'll do a trial run and see how it goes. Is this a disaster waiting to happen?  How do I make sure that my 16 year old buddy doesn't pack his bowls and move out?
Any advice please?

Could you introduce him to their house first, perhaps with them not in it so he is acquainted with their smells?

A long time ago, we had a male cat which we'd got as a kitten.

When he was about four, we got another cat [a female kitten].
He hated her. His behaviour changed and he wouldn't be in the same room with her.
She was more intelligent than him, and she kept out of his way.

Then, one Halloween, she just disappeared. We never saw her again. But the male cat's behaviour changed instantly for the better, and we reckoned that he knew where her body was.

He eventually passed on aged 17.

Then we ended up adopting three feral kittens that had been born in next door's garden shed.
We had them neutered, and at that point found that we had two males and a female.

That was about six years ago, and we still have them.

However, the female is the smallest and nicest, but she is bullied by her brothers.
In turn, the larger male bullies his brother, and sometimes they have fur flying.

So, our conclusion?

One cat is fine.
Two cats may be OK.
More than two cats - No!

We always rub a clean cloth on the new cat then rub doors, skirting boards etc and then put the new cat in one of the bedrooms for a couple of days

After the two days we allow the other cats near the bedroom with the new cat in it

Theres normally a few odd noises and a hisses but once this settles down we let the new cat out to mingle with the others

We have done this everytime and with a little patience its always worked

We had 14 cats at one point, now we are down to 9 and they get on fine, even with the dog

Just take it steady and separate the cats if it gets too much

I hope it all goes well

Mark

Thanks for all your replies.  I've got some herbal "happy juice" which the vet gave me last time Mac got stressed.  Just squirt on his food. Seemed to space him out but he loved it, especially when I put it on half a satchet of wet food ( normally forbidden ).  I've also read that a cat enclosure of some sort is useful just for a few hours at a time.  My sister has a spare large dog cage which could do the trick whilst introductions are taking place.  Fortunately I can shut Mac in the utility room overnight so he has access to the garden as normal,  whilst keeping the new boys in the kitchen. I also think swopping "smelly" blankets a week in advance could be a good idea.
Please keep the tips and advice coming. I'll let you know how it goes.  Paws crossed!