I don't really have any idea that I know works definitely. I've found cats
like to find their own balance. Still. You could try smearing the kitten
with butter to see if the older cat will want to wash it. Isn't a six week
old kitten a bit young to leave its mother?

We had that with two of ours although there was only a year difference. When
we asked the vet, he said let them work it out for themselves. I know,
little help. Is there a way you can try it while looking on? That way the
little one will be protected and they will have the time to work things out.
Come to think of it all 6 of mine began as friendly enemies, now except for
one they've all fallen in line so to speak.

Oh, there may be a reason for the hissing and roaring. When we brought in a
stray with feline tuberculosis, all the others acted that way. So I'd take
the little one to a vet. Nothing's wrong? Go with the first idea.

I had same problem as you, I have 2 cats (both 2 yrs old) and have just
rescued 2 kittens (9 weeks
old).  I couldnt wait to bring them home and introduce my cats to them,
boy was I in for a surprise, my 2 cats looked at the kittens which were
in
a carrier, hissed then ran out of the room. For the first week I was up
the wall trying to keep a normal peaceful household, everytime the cats
and kittens came together, the cats hissed and didnt want to know the
kittens.  Things started to improve after 2 weeks by trying different
methods, it has been approx 6 weeks now since the kittens arrived home
and
all 4 are getting on fine now, they are all eating next to each other and
peace has been restored in my home.
My advice would be take things slowly, keep
the kitten in a seperate room for a couple of days, try swapping the cats
bedding so they can get used to each others smell, brush each cat with
same brush this will swop cats smells, keep to the routine
your cat is used to feeding times, sleep times etc. (cats dont like change
of their normal routine)make
sure it is peaceful and quiet when you introduce them to each other, dont
be put of if there is a little hissing and growling.  Dont forget to give
your cat lots
of love and cuddles so he does not feel left out.
Oh I forgot to mention by getting 2 kittens they fight, play and harrass
each other rather than harrass my 2 older ones.
I'm sure things will turn out fine in the end as the kitten gets a little
bigger.
Good luck and keep us posted
Tina

You didn't specify the sexes, but generally it's
the male that tends to hiss and growl at little
interlopers... it's been my experience that a little
time is all that's needed.

Chuck