Don't worry too much about the hissing and growling. They will work
out how to handle their territory.

I'll never forget the first time I heard Randy growl. It was when Emily
came into the picture as a six week old kitten. Randy was 3 a the time.

They tolerate each other now.

As I write this Emily is sprawled on the carpet next to me. They do
sleep a lot when it's this warm.

Normal behavior for cats.  They'll fight it out for awhile (hissing,
chasing, etc.) and then settle down after territories have been
established.  My two boys fought for a few hours and then became best
friends. 5 years later, they're inseparable.  Good luck!

Hi Chicas!
Fortunately, yours are young enough so they should adapt to each other
better.  It just might take a bit longer since Cali is a bit nervous.

We went through this a year ago.  I had five BIG adult cats, ages 4-10,
and we adopted two 8 week old kittens (I had just lost my beloved cat
Rocky).  We kept the kittens separted from the big cats during the day
but when we were at home we let them out amongst the rest.  There was
some hissing, but there was also a lot of running...oddly enough, by
the big cats from the kittens.  It turned out that the kittens were not
afraid of the big cats at all, which was surprising since a couple of
the big cats can be bullies at times.  We did this for about a two
weeks before we were comfortable enough to leave them all together
during the day.

If you have your two kitties separated at the moment, I would suggest
exchanging their bedding with one another so each can get the others'
scent.  I know this second suggestion may raise a few eye brows, but if
you have two litter boxes, exchange a small bit of waste as well.  In
observing my own cats, they seem to be all about scent.  I have never
seen so much butt sniffing in all my life amongst cats (and here I
thought only dogs did that :)).  It appears to me that they "identify"
one another by smelling one another...some more intensely than others,
I might add!  LOL

You could also hold Trey for a bit then hold Cali afterwards, again
exchanging the scent.  Once that scent becomes normal for them, the
hissing and spitting and growling should start to decline.

I have one kitty, Kona, who is a fraidy cat and hides in my office
closet.  She has her food, water and litterbox nearby and she does come
out to eat and drink when I am in the room, but aside from that, she
seldom leaves the closet.  She is afraid of her own shadow and cannot
stand to be touched, but on occasion I will pick her up to cuddle her
because she is such a beautitul cat.  On one occasion after a quick
cuddling session with Kona, I reached down to pet one of the kittens,
Raskel, now almost a year old, and as I touched her she growled and
hissed at me because she did not recognize Kona's scent.  So what did I
do?  I rubbed my hands all over her and on her nose, then I picked her
up and cuddled her.  Talk about an unhappy kitty! :)

Sometimes, though, cats want to be the "one and only".  When this
happens, and it is usually with older cats, the introduction of another
can be quite exhausting for all.  I had one friend who actually had an
upstairs kitty and a downstairs kitty because of the fighting.  I do
not know how long she tried to get them used to one another or if she
even took the time to introduce them to one another.  I just felt bad
for both kitties because they seemed trapped to me and the upstairs
kitty always got more attention than the downstairs kitty since my
friend was upstairs more.

I applaud you for adopting strays from the shelter.  Although my
husband would probably pop a vein if I were to get another cat, I am
thinking about adopting another from our local Petsmart which works
with the ASPCA and has cats up for adoption.

Hope this helps!
Deeanna

Hi everyone!
 Thanks for all of the advice, it was very helpful! I am happy to say
that Trey has "moved out" of our bedroom and him and Cali are becoming
friends. There is no more hissing or growling, they love to chase
eachother and wrestle. They even cuddle on the couch sometimes! Thanks
again :)

Kristen