I got a new male kitten last night as a playmate for my other older male kitten.
My newer kitten hisses and growls at everything I've gotten him to calm down a little bit around me but he growls and hisses at toys, food, dogs, my other cat and nothing. He always runs to me when he's scared. He's very loving. My older kitten (JD) LOVES him and just wants to play. The younger kitten (Diesel) doesn't want to play. Sometimes he will let JD play with him but 95% of the time he hates it. They both are use to other cats.
Is he still just getting his bearings? should I separate them or what should I do?
They both are unaltered, does that play a role in it?

We foster kittens for our local animal shelter. We've learned that kittens/cats need time to adjust to new situations. Being unaltered I believe could make a difference too. I would separate them for now & slowly keep re-introducing them. When the new kitten hisses Wrap him up as tightly as you can in a blanket without hurting him (like swadling a baby), then quietly talk to him & pet his head. That has worked with all the hissy kittens we've had. Give him extra time & love. Let him adjust to you & his surroundings first, then your other kitten. Good luck.

It will take a while for the cats to adjust to each other, they'll be fine.

Well do they "hand-face" eachother?

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if so then maybe
-Jesus