Total Marrow and Lymphoid Irradiation and Chemotherapy Before DSCT in Treating Patients With High-Risk ALL or AML

Inclusion Criteria: * Participant has the ability and the willingness to sign the informed consent document (for adults only, for participants with mild cognitive abilities may use a legally authorized representative) * Documented (signed) informed consent; the patient, family member and transplant staff physician (physician, nurse, and social worker) meet at least once prior to starting the transplant procedure; 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 forms * Karnofsky performance status \>= 70% =\< 2 * Acute lymphocytic leukemia or acute myelogenous leukemia who are not in first remission or second remission i.e. after failing induction therapy, or in relapse or beyond second remission; (prior therapy with VP-16 and Cytoxan is allowed) * 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 or primed blood stem cells or a 10/10 allele matched unrelated donor; a single allele mismatch at A, B, C, DR or DQ and a killer immunoglobulin-like receptor (KIR) mismatch at C will be allowed; all ABO blood group combinations of the donor/recipient are acceptable * The time from the end last induction, re-induction, or consolidation regimen should be greater than or equal to 14 days from planned start of study treatment; Note: Chemotherapy given within 14 days of planned study enrollment for the purpose of controlling counts is permitted * Total bilirubin =\< 1.5 x upper limit of normal (ULN) OR 3 x ULN for Gilbert's disease * Serum glutamic oxaloacetic transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) =\< 5 x ULN * Measured creatinine clearance \>= 80 ml/min per 24 hour urine collection OR serum creatinine =\< 1.3 mg/dL * Women of child bearing potential only: Negative urine or serum pregnancy test * Pulmonary function tests: Forced expiratory volume in one second (FEV1) and carbon monoxide diffusion capacity (DLCO) (adjusted for Hb) \>= 50% adjusted of predicted normal value * Echocardiogram (ECHO) or multi gated acquisition scan (MUGA): ejection fraction of \>= 50% AND no finding of abnormal wall motion (i.e. report does not indicate that wall motion is "abnormal" or "altered") * Electrocardiogram (EKG) showing no ischemic changes and no abnormal rhythm * Agreement of men AND women-of-child-bearing-potential to use adequate contraception (hormonal or barrier method of birth control or abstinence) prior to study entry and for six months following duration of study participation; should a woman become pregnant or suspect that she is pregnant while participating on the trial, she should inform her treating physician immediately * DONOR ELIGIBILITY: Donor evaluation and eligibility will be assessed as per current City of Hope standard operating procedure (SOP) Exclusion Criteria: * Prior autologous or allogeneic hematopoietic stem cell * Prior radiation therapy that would exclude the use of TMLI * Plans during the trial to receive any other (non-trial) investigational agents, or concurrent biological, chemotherapy, or radiation therapy; (chemotherapy for white blood count control is permitted) * Uncontrolled illness including ongoing or active infection * History of allergic reactions attributed to compounds of similar chemical or biologic composition to etoposide * Patients with other active malignancies are ineligible for this study, other than localized malignancies * Patients with psychological or medical condition that patient's physician deems unacceptable to proceed to allogeneic hematopoietic stem cell transplantation * Women who are planning to become pregnant or breast feed during the trial * Subjects, who in the opinion of the investigator, may not be able to comply with the safety monitoring requirements of the study