Family history is a recognized risk factor in aneurysmal subarachnoid hemorrhage (SAH). The genetic and environmental contributions are actively researched. The authors of this report present a case series of 3 first-degree siblings affected by nontraumatic, angiographically negative SAH. Data in this study suggest that familial predisposition may also apply to spontaneous, nonaneurysmal SAH and that family history should be actively investigated in all such patients. The identification of families with multiple affected members could lead to an improved understanding of the genetic and environmental factors associated with this condition.