Conversational agents (CAs) are increasingly prevalent in children's lives, serving as educational companions, particularly in shared reading activities. While effective for monolingual children's learning, there exists a gap in meeting the unique needs of the rapidly expanding bilingual child population, who face dual challenges of school readiness and heritage language maintenance. Moreover, most current CAs, designed for one-to-one interactions with children, neglect the importance of parents' active participation in shared reading. Our study introduces the development and home deployment of a bilingual CA, integrated within e-books, designed to foster parent-child joint engagement in shared reading, thereby promoting children's bilingual language development. Results of the study indicated high levels of family engagement in co-reading activities over an extended period, with observable language learning gains in children. This study provides valuable design implications for designing effective and engaging CAs for bilingual families.