Was weirdly just thinking about this yesterday. The Lisbon sisters are obviously the core—Cecilia, Lux, Bonnie, Mary, Therese. But the whole book hinges on the neighborhood boys watching them, those now-grown men narrating. They're main characters too, arguably more than any individual sister besides maybe Lux. We see everything filtered through their obsessed, hazy memory. They've built this collective myth out of snippets and rumors.
Cecilia’s the one who starts it, with her first attempt and that eerie, detached diary. Then Lux, the rebel, the one who sneaks out for dates on the roof. The other three blend together more on purpose, like a single unit of fading girlhood. Their parents, especially the mother, are huge, looming presences that shape the entire tragedy. Mr. Lisbon just kind of wilts in the background.
It's less a story with protagonists and more a study of a group phenomenon, you know? The girls as a concept, the boys as witnesses. Makes it haunting in a specific way regular character arcs wouldn't.