Congenital absence of the teeth, affecting both physiognomy and mastication, can have a great impact on patients' quality of life. It may appear unilateral or bilateral; frequently, it associates with certain general conditions. Familial hypodontia in clinically healthy patients is rare. Genetic transmission, as a determinant factor in missing teeth, can be autosomal dominant, recessive, or related to the sex chromosomes. In case of congenitally missing permanent teeth, the corresponding deciduous teeth can be still found on the arch at adult age. The aim of this article is to present rare cases of familial non-syndromic unilateral and bilateral hypodontia in Romanian adult siblings, highlighting also a cross gene transmission between aunt and niece and evaluating the treatment options in accordance with patient's age and oral status. It shows that early diagnosis of hypodontia is crucial for the patient's future oral health. The decision to keep the temporary teeth or to extract them is influenced by the presence and status of the deciduous teeth, patient's access to treatment and parent's agreement. Asymptomatic adult patients, in which hypodontia was diagnosed during a routine control, do not usually solicit therapeutic intervention until the deciduous teeth are also lost; still, in situations where complications arise through their loss, the treatment of hypodontia is complex, involving a close collaboration between a team of specialists. The article also includes a detailed review of literature referring to the prevalence of hypodontia among different populations.