Allogeneic Stem Cell Transplantation for Multiple Myeloma and Myelofibrosis

Inclusion Criteria: * Eastern Cooperative Oncology Group (ECOG) performance status 0-1 * Participants must have one of the following diagnoses of multiple myeloma (MM) or primary/secondary myelofibrosis (MF) * Participants must have histologically documented multiple myeloma (MM) * Participants in early relapse (less than 24 months from initiation of systemic anti-myeloma therapy which may include single or planned tandem autologous transplant) after primary therapy that included and autologous HSCT; OR * Later stage; OR * High risk factors defined by the presence of any one of the following detected at any time prior to enrollment: deletion of chromosome 13 by conventional cytogenetics, hypodiploidy, abnormality in chromosome 1 (1q amplification or 1p deletion), t(4;14), t(14;16), t(14;20) or deletion of 17p by fluorescence in situ hybridization (FISH) or conventional karyotyping; high risk criteria based on commercially available gene expression profiling; OR * Extramedullary disease, plasma cell leukemia or high lactate dehydrogenase (LDH) * Participants must have histologically documented myelofibrosis (MF) * Participants with Dynamic International Prognostic Scoring System (DIPSS) plus intermediate stage 2 or higher risk MF; OR * Subset of intermediate stage 1 participants; defined by: * Poor-risk molecular profile (triple negative: JAK2, CALR, MPL); OR * Presence of any of the following mutations: ASXL1, SRSF2, EZH2, IDH1/2; OR * Severe thrombocytopenia, severe anemia, high peripheral blood blasts percentage; OR * Unfavorable cytogenetic abnormalities (rearrangements of chromosome 5 or 7 or \>= 3 abnormalities * Able to provide informed consent and willing to sign an approved consent form that conforms to federal and institutional guidelines * DONOR: A related donor - fully matched * DONOR: A related donor - haploidentical * DONOR: An unrelated donor - fully matched * DONOR: An unrelated donor -9/10 matched Exclusion Criteria: * Cardiac-left ventricular ejection fraction \< 40%, symptomatic coronary artery disease, or uncontrolled arrhythmias * Pulmonary-forced expiratory volume at one second (FEV1) or diffusion capacity of lung for carbon dioxide (DLCO) \< 40% or history of chronic use of supplemental oxygen. Temporary use of supplemental oxygen at the time of screening or registration is allowed if the investigator feels that the underlying cause of requiring oxygen is reversible by the time treatment begins. * Renal-calculated or measured glomerular filtration rate (GFR) \< 30 ml/min, dialysis-dependent, or history of renal transplant * Hepatic-bilirubin \> 2 X upper limit of normal (ULN) * Alanine aminotransferase (ALT) \> 2.5 X ULN or cirrhosis * Participants with active or uncontrolled bacterial, viral, or fungal infections requiring systemic therapy * Pregnant women, nursing mothers or women of child-bearing potential who are unwilling to use medically accepted methods of contraception * Male and female subjects not willing to agree to medically accepted methods of contraception