- The subject has a history of inhibitor and has one or more full brothers with severe hemophilia A, with or without an inhibitor, who are eligible for and have agreed to be in the study, and two parents who have agreed to be in the study or the subject does not have a history of inhibitor but has one or more full brothers with severe hemophilia A and a history of inhibitor who are eligible for and have agreed to be in the study, and two parents who have agreed to be in the study.