In The Sound of Music, Maria cares for seven von Trapp children. The children are Liesl, Friedrich, Louisa, Kurt, Brigitta, Marta, and Gretl, with Liesl as the eldest and Gretl as the youngest.
The 1965 film stars Julie Andrews as Maria and Christopher Plummer as Captain Georg von Trapp. Maria begins as a postulant at Nonnberg Abbey before becoming the children’s governess. Her warmth, music lessons, and playful approach gradually soften the household’s strict atmosphere, leading to the family’s famous singing career and escape from Austria after the Anschluss.
The number seven refers to the children in the film’s fictionalized family, not to Maria’s biological children. The movie was inspired by Maria von Trapp’s memoir, but it changes names, ages, chronology, and several family details for dramatic effect. In real life, Maria was hired to tutor one sick child and later became the children’s stepmother. The film’s seven-child household is therefore the canonical answer for this question.