Does a donor have to have the same blood group as the patient?

For blood stem cell transplants, what matters is not so much the same blood group but the best possible match between the tissue characteristics from the donor and patient. A perfect match is very complicated to find and much like looking for a needle in a haystack. When blood stem cells are transplanted, the recipient acquires the same blood group as the donor.

At most, your blood group would be an additional factor in your selection.