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 stud…