Combination Chemotherapy, Total Body Irradiation, and Donor Blood Stem Cell Transplant in Treating Patients With Secondary Myelofibrosis

Inclusion Criteria: * Diagnosis of primary of secondary myelofibrosis with transplant indication by Dynamic International Prognostic Scoring System (DIPSS)-plus (\> intermediate-1) * Patients \>= age 50 must have a comorbidity score (hematopoietic cell transplant-comorbidity index \[HCT-CI\]) \< 4 (Sorror) * Patients can be in chronic phase (CP) with bone marrow (BM) blast count =\< 15% as long as no evidence of disease acceleration per principal investigator (PI) and treating physician's opinion or after progression to acute myeloid leukemia (AML) and achieved =\< 5% BM blasts (morphologic complete remission \[CR\] prior to transplant) * Lack of an human leukocyte antigen (HLA) matched donor or need to proceed fast to transplantation when a patient does not have an immediately available matched unrelated donor (typed by high-resolution in the registry) * Performance status \>= 70% (Karnofsky); patients \> 50 years should have adequate cognitive function; any concerns regarding cognitive function should be addressed by a geriatrician/neurologist * Alanine aminotransferase (ALT)/aspartate aminotransferase (AST)/bilirubin =\< 5 X upper limit of normal (ULN) * Measured creatinine clearance \> 60 mls/min * Left ventricular ejection fraction (LVEF) \>= 50% * Corrected carbon monoxide diffusing capability (DLCOc) \>= 50% * No active infections * Prior treatment with JAK2 inhibitor therapy is not excluded; a JAK2 inhibitor will need to be stopped 1-2 days prior to starting conditioning regimen * DONOR: Documented informed consent per local, state and federal guidelines * DONOR: Genotypically haploidentical as determined by HLA typing * Preferably a non-maternal HLA haploidentical relative due to data of high incidence of graft failure with use of maternal HLA haploidentical cells * Eligible donors include biological parents, siblings or half-siblings, children, or cousins in rare instances * DONOR: Absence of pre-existing donor-specific anti-HLA antibodies (DSA) in the recipient; Patients with pre-existing DSA could undergo desensitization per City of Hope (COH) standard operating procedures \[SOP\] and should have DSA \< MFI of 2000 prior to conditioning at discretion of PI * DONOR: Infectious disease screening performed within 30 days prior to stem cell mobilization per federal guidelines and is: * Seronegative for HIV 1+2 antibody (Ab) and/or HIV polymerase chain reaction (PCR), human T-cell leukemia virus (HTLV) I/II Ab, hepatitis B virus surface antigen (HBsAg), hepatitis B virus surface antibody (HBcAb), hepatitis C virus (HCV) Ab * Negative rapid plasma reagin (RPR) for syphilis * DONOR: Women of childbearing potential (WOCBP): Urine pregnancy testing performed within 7 days prior to stem cell mobilization * DONOR: Is approved and completed evaluation prior to recipient initiation of the preparative regimen per institutional guidelines Exclusion Criteria: * Evidence of severe portal hypertension with evidence of decompensation either with bleeding varices, large volume ascites, or hepatic encephalopathy * In a bone marrow biopsy 4 weeks prior to start of conditioning on study: * \> 15% bone marrow blasts at transplant if no history of AML and per PI and treating physician's opinion of disease acceleration * \> 5% if had previous progression to AML * Human immunodeficiency virus (HIV) positive; active hepatitis B or C * Patients with active infections; the PI is the final arbiter of the eligibility * Patients with evidence of severe pulmonary hypertension by echocardiogram and confirmed by a subsequent right side cardiac catheterization pre-enrollment * Liver cirrhosis * Prior central nervous system (CNS) involvement by tumor cells * History of another primary malignancy that has not been in remission for at least 3 years (the following are exempt from the 3-year limit: non-melanoma skin cancer, fully excised melanoma in situ \[stage 0\], curatively treated localized prostate cancer, and cervical or breast carcinoma in situ on biopsy or a squamous intraepithelial lesion on papanicolaou \[PAP\] smear) * Positive beta human chorionic gonadotropin (HCG) test in a woman with child bearing potential defined as not post-menopausal for 12 months or no previous surgical sterilization * Noncompliance - inability or unwillingness to comply with medical recommendations regarding therapy or follow-up, including smoking tobacco * DONOR: Has undergone solid organ, stem cell, bone marrow or blood transplantation * DONOR: Receiving any investigational agents, or concurrent biological, chemotherapy, immunosuppression or radiation therapy * DONOR: Active infection * DONOR: Thrombocytopenia \< 150,000 cells /mm\^3 at baseline evaluation * DONOR: Sero-positive for HIV-1 \& 2 antibody, HTLV-I \& II antibody, hepatitis B virus (HBV) and HCV * DONOR: Medical or physical reason which makes the donor unlikely to tolerate or cooperate with growth factor therapy and leukapheresis * DONOR: Factors which place the donor at increased risk for complications from leukapheresis or G-CSF therapy * DONOR: WOCBP: Pregnant or =\< 6 months breastfeeding