Malignant infantile osteopetrosis (MIOP) is a rare fatal genetic disorder that is characterized by the bone's inability to regulate remodeling. The only curative therapy is hematopoietic stem cell transplantation. Stem cells provided from an HLA identical matched sibling donor is the standard of care, but not feasible for the majority of patients. In addition, due to the potentially rapid progression of this disease, the time to identify a suitable HLA matched unrelated donor is not optimal. Therefore this study is designed to test the hypothesis that children with osteopetrosis can properly engraft hematopoietic stem cells that are donated from a partially matched parental donor, or "haploidentical" stem cell donor that are processed on the investigational device, CliniMACS selection system.