Ehlers-Danlos syndromes (EDS) are a group of diverse hereditary connective tissue disorders. Various EDS subtypes present as different diseases. Periodontitis of early onset is a major criterion of periodontal EDS (pEDS). This article reports the clinical case of two siblings, young adults, who came to the clinic for diagnosis and treatment of periodontal disease. The patients had already been diagnosed with pEDS several months earlier after being referred for genetic testing by a dermatologist. It should be noted that in these siblings pEDS had been misinterpreted for years by health care specialists despite the patients’ periodontal disease, which had appeared at the age of 3 years. The subsequent effects of periodontal disease in these patients jeopardized the survival prognosis of their teeth. It may be stated that, in spite of pEDS’s status as a rare syndrome, the dental practitioner can play a key role in the early diagnosis by responding appropriately to periodontal manifestations at early stages. (Quintessence Int 2021;52:166–174; doi: 10.3290/j.qi.a45263)