In order for someone's stem cells to be used on another person, do they have to be related?

No, but a good match: Allogeneic stem cell transplants (allografts) refer to stem cells that are taken from one person and given to another. Currently, these types of transplants are performed in research studies (clinical trials). Doctors want to avoid graft-versus-host disease (gvhd), which is a serious complication that can occur with allogeneic transplant, s if the transplant attacks the patient's cells.

No: Stem cells are immunologically privileged, meaning they are not recognized by the body's defense system as foreign. Stem cell transplants can be successful using allogenic cells (same species, different individual) and xenogenic cells (different species). However, the fda currently allows the use of only autologous cells (your own).