The social science that would study the family structure of the Romans is called "Roman Family Studies" or "Roman Family History". This field of study would examine various aspects of the Roman family, including its structure, function, and roles of different family members in the society. It would also analyze the legal system, economic aspects, and religious practices related to the Roman family. Scholars in this field use various sources, including historical records, literature, and archeological findings to gain a comprehensive understanding of the Roman family structure.