The dissertation presents a pioneering investigation into child speech among Bikolano children. It aims to address the underdescription and underdocumentation of Child Bikol as spoken in the Philippines. Bikol, an Austronesian macrolanguage, often coexists with more dominant languages, making Bikolano children both emergent multilinguals and heritage speakers. The study uses a longitudinal corpus sample from multiple Bikol-using children to examine language acquisition through the lenses of speech production, concentrating on vocabulary and morphosyntactic development. Vocabulary development analysis explores child forms and the acquisition of words, while morphosyntactic development investigates voice and agreement in Child Bikol. By investigating language acquisition in multilingual contexts and in underrepresented languages, this dissertation contributes to our knowledge of emergent multilingualism and heritage language acquisition. It forms part of a broader effort to construct a corpus of child-directed speech and child speech among Bikolano and other Austronesian families, enriching our understanding of language development and intergenerational transmission in diverse linguistic environments. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]