This study explores the kinship terminology of Proto-Tupí-Guaraní (PTG) through an interdisciplinary perspective that draws on ethnology, historical linguistics, and the ethnography of Tupi-Guaranian peoples. Inferences about cultural prehistory are made through phylogenetic comparative methods, a suite of computational tools for exploring evolutionary change in related populations, applied to a dataset of kinship terms from 24 Tupi-Guaranian languages. The study outlines the coding procedure for typological data, along with the parameters, inputs, and assumptions of the evolutionary models. Parsimony-based ancestral state inference is used to reconstruct a number of typological features of the kinship system of PTG, such as fusion and bifurcation in the first ascending generation (+1), relative age and sex-based distinctions in sibling terminology, and terminological equation between siblings and parallel cousins. The current state of reconstruction of the linguistic forms for kinship terms in PTG is reviewed, and these forms are mapped onto the system inferred through comparative analysis. This proof-of-concept study demonstrates the utility of phylogenetic analysis for inferring kinship structures in ancestral language communities.