Sounds like you just have similar premises, which really doesn't matter. Don't worry about it. It's unlikely that many of your readers will have read the other comic, and even if they do, they might not notice the similarities unless they're very specific.
, I think Hjels meant not the general premise, but the underlying deeper theme - for example, is one story about acceptance, while the other is about friendship? If so, then you definitely have nothing to worry about because the themes are different. If they're similar, then people might notice, but it's still not a problem as long as you're not ripping off any specifics from the other story.
And by beats, Hjels means scenes in your story where something important (to the characters/story) happens, and the order this happens in. Here's an example of a beat structure:
If both stories have similar beats and in roughly the same order, then they're likely to come off as similar.
There is nothing new under the sun and I'm sure that for every story you write, there are already five others that have very similar stories. That's okay
. What makes your story unique is what you put into it
. Make it yours; do what you want to do, and do it well.