Inclusion Criteria:

          -  Primary or secondary myelofibrosis intermediate or high risk by Dynamic International
             Prognostic Scoring System (DIPSS) in chronic or accelerated phase

          -  Performance status of >= 70% on the Karnofsky scale

          -  The effects of chemotherapy, ruxolitinib on the developing fetus are unknown; for this
             reasonWomen of child-bearing potential and men must agree to use adequate
             contraception (hormonal or barrier method of birth control or abstinence) prior to
             study entry and for 1 year following transplant as per City of Hope standard operating
             procedure (SOP) for allogeneic transplantation; should a woman become pregnant or
             suspect that she is pregnant while participating on the trial, she should inform her
             treating physician immediately

          -  Bone marrow and peripheral blood studies must be available for confirmation of
             diagnosis; cytogenetics, flow cytometry, and molecular studies (such as JAK-2, MPL and
             CALR mutational status) will be obtained as per standard practice

          -  Bone marrow aspirates/biopsies should be performed within 30 +/- 3 days from
             registration to confirm disease remission status

          -  All candidates for this study must have a human leukocyte antigen (HLA) (A, B, C, DR)
             identical siblings who is willing to donate bone marrow for primed blood stem cells or
             an 8/8 allele-matched unrelated donor

          -  All ABO blood group combinations of the donor/recipient are acceptable since even
             major ABO compatibilities can be dealt with by various techniques (red cell exchange
             or plasma exchange)

          -  A cardiac evaluation with an electrocardiogram showing no ischemic changes or abnormal
             rhythm and an ejection fraction of 50% established by multi-gated acquisition scan
             (MUGA) or echocardiogram

          -  Patients must have creatinine of less than or equal to 1.5 mg/dL or creatinine
             clearance > 60 ml/min

          -  A bilirubin of up to 2.0 mg/dL, excluding patients with Gilbert's disease

          -  Patients should also have a serum glutamic oxaloacetic transaminase (SGOT) and serum
             glutamate pyruvate transaminase (SGPT) less than 5 times the upper limit of normal

          -  Pulmonary function test including diffusion capacity of the lung for carbon monoxide
             (DLCO) will be performed; forced expiratory volume in 1 second (FEV1) and DLCO should
             be greater than 50% of predicted normal value

          -  All subjects must have the ability to understand and the willingness to sign a written
             informed consent that has been approved by the City of Hope Institutional Review Board
             (COH IRB); the patient, a family member and transplant staff physician (physician,
             nurse, social worker) will meet at least once prior to the subject signing consent;
             during this meeting all pertinent information with respect to risks and benefits to
             donor and recipient will be presented; alternative treatment modalities will be
             discussed; the risks are explained in detail in the enclosed consent form

          -  Prior therapy with hydroxyurea, interferon, anagrelide, ruxolitinib, hypomethylating
             agents, revlimid, thalidomide, steroids, other JAK inhibitors is allowed; for acute
             myeloid leukemia (AML) patients who are back in chronic phase myeloproliferative
             neoplasm (MPN), prior induction therapy is allowed

        Exclusion Criteria:

          -  Patients should not have any uncontrolled illnesses including ongoing or active
             infection

          -  Patients may not be receiving any other investigational agents, or concurrent
             biological, chemotherapy, or radiation therapy

          -  History of allergic reactions attributed to compounds of similar chemical or biologic
             composition to ruxolitinib

          -  Pregnant women are excluded from this study because ruxolitinib is an agent with the
             potential for teratogenic or abortifacient effects; because there is an unknown but
             potential risk for adverse events in nursing infants secondary to treatment of the
             mother with ruxolitinib, breastfeeding should be discontinued if the mother is treated
             with ruxolitinib

          -  Patients with active 2nd malignancies other than myelofibrosis, AML, excised skin
             cancer, early stage cervical and prostate cancer

          -  Previous allogeneic hematopoietic stem cell transplantation

          -  Any psychiatric, social or compliance issues that, in the treating physician opinion,
             will interfere with completion of the transplant treatment and follow up

          -  Patients who have been treated with chemotherapy or radiation within two weeks of
             planned study enrollment; this does not include hydroxyurea, which may be continued
             until start of conditioning therapy; ruxolitinib may be continued at principal
             investigator's discretion during conditioning

          -  Non-compliance; defined as any subject, who in the opinion of the investigator, may
             not be able to comply with the safety monitoring requirements of the study