Number of named characters in my illustrated nonfiction

At some point during the revision stage of Fairy Spell: How Two Girls Convinced the World That Fairies Are Real, I realized it was longer than my other picture book nonfiction. (I probably did compare word counts, though I don't remember the results.) 

Then I realized it was longer partly because that story required more named characters—meaning characters important enough to my telling that I should refer them to by name rather than connection (i.e. "Jerry's father," in Boys of Steel: The Creators of Superman) or title. Generally speaking, if a character appears only once, s/he need not be identified by name.

Not including fictional characters like Batman or historical figures mentioned but not an active character in the story, like Edgar Allan Poe in Bill the Boy Wonder: The Secret Co-Creator of Batman and President Kennedy in Thirty Minutes Over Oregon: A Japanese Pilot's World War II Story, this is how many named characters my illustrated nonfiction books include:

• Boys of Steel—two (Jerry Siegel, Joe Shuster)
• Bill the Boy Wonder—eight (Bill Finger, Bob Kane, Vin Sullivan, Jerry Robinson, Portia Finger, Fred Finger, Julius Schwartz, Jerry Bails)
• Thirty Minutes Over Oregon—four (Nobuo, Ayako, Yoshi, and Yoriko Fujita)
• Fairy Spell—eight (Frances Griffiths, Elsie Wright, Polly Wright, Arthur Wright, Arthur Conan Doyle, Edward Gardner, Harold Snelling, Fred Gettings)

So at eight, Fairy Spell has the same number as Bill the Boy Wonder, but at one point it had eleven. During rewrites, three disappeared—much like fairies themselves are prone to do.