Children's writing development is a matter of concern for Australian and other education systems. Factors related to the nature of writing as a literate skill, school writing pedagogy, and diminishing role of writing in a screen-dominant environment may account for this educational concern. What happens in a child's writing when immigrant parents assign them writing tasks at home taking into account their writing concerns compounded by their family linguacultural backgrounds in an English-only environment? This paper presents developmental corpus analyses involving data taken from a 1.5-year family writing intervention program for a primary school immigrant child, using multidimensional analysis to determine the latent linguistic traits characteristic of the child's writing development over time. The findings illustrate a range of linguistic features comprising four main dimensions representative of the child's writing development, together with a focus on the emergence of his written self. Although the findings provide data-driven developmental insights into the child's writing life, the parental intervention itself presented ethical dilemmas.