I've recently introduced 3 moggy kittens to my 18 month old Dolly. I won't pretend it all went smoothly - she disappeared for 3 days, she refused to be in the same room as them and was generally grumpy but day by day things improved and she started to accept them. They don't snuggle up together but there's no aggression and they do play an eat together.
My main advice would be to be patient. Supervise the initial contact until you're sure they're not going to harm each other and put them in separate rooms if you're not sure or not able to supervise all the time. Don't be put off if there are growls and hisses to start with, that's part of the process and you only need to worry if it becomes violent. Find toys and treats that they can share so that they associate each other with good things, give them both lots of individual attention, swap bedding so that they get used to each other's smell. Post lots of pictures on here