Sometimes when I make a new character who's design is very similar to a central characters I have in something else I make an active point to add little details and nuances to make them stand out from each other. Though these are novels, so people can imagine them mostly how they like based on the descriptions, I still find it useful to have enough detail to give people a clear impression of their appearances, and that often means me being like "...hmm, how can I switch up their complexion, style, eye shape, body type, etc to be a little more different than this other character?"
In the end there are a limited amount of features in the world and people are all pretty alike in one way or another, but I still like to imagine having an array of different-looking characters if I ever lined them all up beside each other.
I don't think I have any other central characters that look a lot like my female lead from "Damsel in the Red Dress" but I did worry about Mrs. Moon looking a bit too much like Juana King, so I made sure to add details that would make them stand out from each other even when you're just reading their descriptions.
I think my newest female lead, Essence Walker from "A Dozen Morning Glories" looks a lot different from my female lead from "Damsel in the Red Dress" Alicia in almost every way, but though I see them quite differently in my head, I questioned how differently the male leads will sound just based off of brief/cursory descriptions, so I made sure to add more detail in my understanding of their face shapes, features, builds, hair styles, complexions etc.
If you have this struggle how do you balance/fix it when working out your designs? Or do you not worry about it?
If you don't have this struggle, how does your character designing process tend to work?