The emergence approach to speech acquisition theorises the influence of intrinsic capabilities (e.g., maturation), interactional capabilities, and extrinsic contexts (e.g., ambient phonology). Intrinsic and extrinsic influences were examined via a case study of a 3-generation Vietnamese-English family with two brothers (C1 aged 5;6 and C2 aged 3;10), their mother (M), grandfather (GF) and grandmother (GM). Their speech was assessed using the Diagnostic Evaluation of Articulation and Phonology (DEAP) and the Vietnamese Speech Assessment (VSA). Standard Australian English/Standard Vietnamese productions were defined as ‘correct’, even though the adults spoke different Vietnamese dialects. Their percentage of standard consonants correct (PSCC) was: C1 (English:92.27%, Vietnamese:89.05%), C2 (E:86.47%, VN:86.13%), M (E:90.34%, VN:96.35%), GF (E:82.61%, VN:97.81%), GM (VN:99.27%). Percentages were higher when dialectal variants were included. C1 and C2 had more pronunciation matches with English (86.96%) than Vietnamese (79.56%). C1’s pronunciation matched: M (E:85.02%, VN:83.94%), GF (E:79.23%, VN:77.37%), GM (VN:73.72%) and C2’s pronunciation matched: M (E:79.23%, VN:73.72%), GF (E:73.91%, VN:75.18%), GM (VN:72.26%). There was evidence of ambient phonology influences and cross-linguistic transfer. For example, in Vietnamese ‘r’ is produced as /ʐ/ or /r/, but was produced by C1 as [ɹ] (English approximant) and by C2 [w] (age-appropriate/ɹ/substitution). The children demonstrated maturation influences for late-occurring English consonants (e.g., English /θ/ →[f]). This study found evidence for the emergence approach and recommends knowledge of the ambient phonology augments traditional child-focused understandings of children’s speech acquisition.