Strategic clinical assessment of a patient’s close family members aids diagnosis by adding valuable information to the family history. A, When 18-year-old Patient A (arrow) presented with mild left ventricular (LV) hypertrophy, his family history of sudden cardiac death (I-3 and II-7) raised suspicion for HCM. B, Clinical cardiology evaluation of the patient’s mother (III-2) and sisters (IV-2 and IV-3) provided the evidence needed for diagnosis. Circles indicate females; squares, males; slash, deceased. HCM = hypertrophic cardiomyopathy.