Old cats don't like new kittens

Hi, I'm new here and I recently adopted 2 boy kittens and 1 girl kitten (now 4mo old) and my other 4 cats (1yr in Oct.) do not like them AT ALL. The older cats are outside except for during the day (they're supposed to kill the mice and moles at night XD) and the little ones live inside and I often times get woken up by the sound of hissing cats. Any suggestions on how to get them to at least tolerate each other? Thank you!

Welcome to TCS! [emoji]128522[/emoji]

Here are a couple of links to check out:

http://www.thecatsite.com/a/the-multi-cat-household

http://www.thecatsite.com/a/introducing-cats-to-cats

It all takes time!

Are your cats and kittens all neutered and spayed?