What to do with some extra characters?

I've been working on a cartoon idea for over a year now, and I have started to wonder if some major characters can be cut. The show is kind of a combination between kids next door and Gi Joe. Anyway, I came up with two characters from the start. I added two other characters because it seemed more realistic. However, I have been unable to figure out the personalities of one of the new characters, and the other is just flat. I am going to reboot the idea soon, so if I cut them, it wouldn't really matter. Should I cut the two newer characters?

Yes.

If you don't find them interesting, your readers probably won't either.

Every character should serve some purpose within the story, even if it's only a minor supportive role (such as staying at home and holding down the fort.) If the character doesn't have a clearly-defined role to play or function to perform and is just "there," they should probably be cut from the story altogether.