Xiomara is a 15-year-old Afro-Latina living in Harlem who uses her leather notebook to write poetry about the feelings she cannot express out loud. She possesses a mature figure that attracts unwanted attention, making her feel self-conscious and quick to defend herself. Despite her combative exterior, she is deeply sensitive, inquisitive, and trying to balance her evolving identity with her mother's strict religious expectations.

Xavier is Xiomara's twin brother, older by fifty minutes. He is physically smaller than his sister, gentle, academically gifted, and attends a special high school for talented students. Unlike Xiomara, he is naturally devout and adheres more closely to their mother's Catholic expectations, though he harbors his own private life and interests.

Mami is an immigrant from the Dominican Republic who works as a cleaner to support her family. As a devout Catholic who once wanted to be a nun, she strictly enforces religious rules in her household. She imposes rigorous expectations on Xiomara, viewing the outside world as a threat to her daughter's purity.

Aman is Xiomara's biology lab partner and her first serious romantic interest. He lives with his father, having immigrated from Trinidad, and bonds with Xiomara over their shared love of music and her poetry. He is a gentle and affectionate young man who encourages Xiomara to share her creative voice.

Papi is the twins' father, who works for the Transit Authority and frequently travels back to the Dominican Republic. An ex-womanizer who reformed his ways after his children were born, he provides for his family financially but remains emotionally disengaged from the household.

Caridad is Xiomara and Xavier's lifelong best friend. She easily follows the rules of the Catholic church and represents everything Xiomara's parents want in a daughter, yet she never judges Xiomara's doubts. She acts as a thoughtful, graceful, and fiercely loyal confidante to both twins.

Father Sean is the head priest at La Consagrada Iglesia Catholic Church. Originally from the West Indies, he leads the youth Bible study and confirmation classes. He is perceptive enough to notice Xiomara's internal conflicts and tries to encourage her to speak openly about her doubts rather than simply punishing her.

Ms. Galiano is a young, confident Latina English teacher at Chisholm High School. She quickly recognizes Xiomara's talent for writing and persistently invites her to join the spoken-word poetry club. She serves as a vital role model and mentor for the aspiring poet.

Isabelle is a straight-talking student from the Bronx and a member of the school's spoken-word poetry club. She has a curly blond afro and a delivery style that reminds Xiomara of a rapper, quickly becoming a welcoming peer to Xiomara in her artistic journey.

Cody is a tall, red-haired student who attends the same school for gifted students as Xavier. He develops a close relationship with Xavier, prompting Xavier to step away from his sister's constant physical protection.

Marcy is a student in Xiomara's biology class. She takes over as Xiomara's lab partner when seating arrangements are changed in the classroom.

Chris is a member of the spoken-word poetry club who performs for the English class to advertise an upcoming competition. He is a fast talker with a loud, energetic presence.

Stephan is a member of the spoken-word poetry club. His writing style is visual and precise, landing clearly on its target when he performs for the group.