Persistence and dilation of the embryologic thyroglossal tract gives rise to the condition of thyroglossal duct cyst. Although these cysts have an embryologic origin, there is rarely a history of inheritance. A search of the literature shows only two family reports, which includes a total of nine patients. We report on a third family with thyroglossal duct cyst in two members. The patients were female siblings aged 2 and 6 years, both of whom underwent successful surgical excision of their thyroglossal duct cysts by modified Sistrunk's technique.