Idiopathic myelofibrosis (MF) is a rare disease in childhood. The clinical spectrum is very variable. Familial idiopathic MF has been recorded exceptionally. In previous reports idiopathic MF in childhood has been described in association with congenital anomalies and with chromosome abnormalities, although neither of these features have been reported in a familial context. We report two sisters with idiopathic MF and multiple eruptive hemangiomas. Details of their clinical signs, laboratory findings, and histologic features are described.