Resident Kitten Growling at New Kitten

There is really nothing you can do other than separating them and slowly reintroducing them each day. Although, letting nature take its course (with your supervision, of course) is really the only way this will happen.

Give them time. "Old" kitten will end up loving "New" kitten. Every time you pick up the new one, talk kindly to the first, and stroke her.

I have older cats, one of them a stray I recently took in. My poor first cat still growls and complains when he gets too close, and I've had him two years now. He adores her, of course, thinks she's the queen. And I think she makes a fuss simply to maintain that royal position!

Your cats will forget that they're not related soon, and then just squabble like any other siblings!