The purpose of this research study is to look into the factors that affect the second language learning of the six multicultural children from three families whose birth mother came from the Philippines. All the mothers can speak three languages like Tagalog (Philippine's heritage language), English, and Korean. The fathers of the multicultural children are all Korean men and can only speak their native language. The mothers were the first to participate in the interview followed by the two children. Parent interviews and children interviews, as well as child observations, are included in the data collection. Qualitative data analysis has the following results: (1) The critical period for second language learning of multicultural children is vital especially on their pronunciation and communication skills; (2) Filipino mother's role as a second language input provider during childhood is very effective but becomes weaker if not done in continuum; (3) financial stability can be one of the reasons why mothers cannot pay attention to their children's learning and they cannot attend academies particularly when they reach middle school or high school that cause them difficulties in learning and analyzing English grammar. The results emphasize that Filipino mothers need to be informed and aware of the advantages they have on steadily teaching their children their native language. At the same time, Korean society also has the responsibility to support them on this issue.
