What do you suggest if my brother has hodgkins lymphoma and he had a bone marrow transplant and got gvhd, what will happen now?

Immune reaction: Graft versus host disease (GvHD) occurs following an allogeneic bone marrow transplant where donated marrow cells view your brothers body as foreign, and attack his body. A Factor that increase acute GvHD, is the HLA match, which causes donor cells to recognize recipient cells as foreign, leading to an immune response.This causes an increased risk of infection, rash etc treated with steroids

Depends on severity : Low grade of gvhd may not be that bad in terms of prognosis. It may actually signify graft vs lymphoma affect. Poorly controlled high grade of gvhd is not good.