How parent-child interaction effectively supports children's bilingual heritage language development in a shared book-reading practice is an under-researched area. The in-depth study reported in this paper examined an episode of one child, a four-year-old girl and her father, reading an English story in Chinese. Approximately 70 hours of video observations were collected over nine months and analysed in order to understand how families used storybook reading to support heritage language development. Vygotsky's cultural-historical concepts of motives and conflicts form the foundation of the analysis. The study found that "two-way" engagement when reading a book, elaborations that went beyond the immediate text and creative playful abstractions connected to family practices all contributed to supporting heritage language development. It is argued that shared book reading not only illustrates effective family pedagogical practices for heritage language development, but also offers insights into building pedagogical practices for early years education.