出てこないと気持ちは落ち着かない meaning > My western brain can't comprehend the final part of the sentence! I know is something like "show up" and something like "calm down, harmonize".

= not to feel at ease.

Thus



can be translated into something like

"I would not feel at ease if Neville Longbottom didn't show up, even if Ron and Hermione do (did?) in the Harry Potter series."