If it's possible, you could do a little bio for each character with that info in a tab in the main menu and maybe label when info gets spoilerish. Personally the only info I'd like to know is pronouns, because I agree with finding things out through the story. With bios, people can read if they want and ignore if they don't.
However, I'm not a game dev and don't know how much work that would be.
Also thank you for the fanservice!