Donor Bone Marrow Transplant With or Without G-CSF in Treating Young Patients With Hematologic Cancer or Other Diseases

Inclusion Criteria: * Diagnosis of hematologic cancer or other disease, including any of the following: * Chronic myelogenous leukemia in first or second chronic phase * Acute lymphoblastic leukemia (ALL), meeting any of the following criteria: * Relapsed ALL enrolled on a Children's Oncology Group (COG) relapse clinical trial OR received ≥ 1 round of reinduction therapy (4-6 weeks) and 1 round of intensive consolidation chemotherapy (3-6 weeks) * ALL in second complete remission (CR)\* after a bone marrow, extramedullary, or combined bone marrow and extramedullary relapse * Very high-risk ALL in first CR, defined as any of the following: * Philadelphia chromosome-positive ALL * Hypodiploidy (\< 44 chromosomes) * Mixed lineage leukemia rearrangement * Induction failure * Acute myeloid leukemia in first or second CR * Induction therapy must be completed * Juvenile myelomonocytic leukemia * Myelodysplastic syndromes * No clinically evident CNS or extramedullary disease * No blasts seen on cerebrospinal fluid cytospin * Post-relapse reinduction therapy must be completed * Not planning to receive reduced-intensity conditioning regimen * Not planning to receive a graft that has undergone T-cell depletion * No Down syndrome * Matched sibling donor must be available and must be enrolled on ASCT0631D companion study * Karnofsky performance status (PS) 60-100% (patients \> 16 years of age) OR Lansky PS 60-100% (patients ≤ 16 years…