The illegitimate son of the late Dr. Albert Wesker, Muller was born and raised in 1992 at Edonia by his mother in order to respect his father. Muller was an interest to Carla Radames and The Family who sought the man for his superior antibodies inherited from his father. He would later develop a partnership with Sherry Birkin, a Division of Security Operations agent sent to evacuate Muller for vaccine research.