RecruitingDrug trialRuxolitinib-Enhanced Haplo HCT for Children and Young Adults With Sickle Cell DiseaseThis trial will determine whether adding ruxolitinib to a reduced intensity conditioning (RIC) regimen reduces the rate of graft failure following haploidentical (haplo) hematopoietic cell transplant (HCT) for children and young adults with sickle cell disease (SCD). This study will enroll and treat up to 24 participants. Recruitment is expected to last for about 2 years and participants will be followed for an additional 2 years post-HCT.