The Thomas family, also referred as the "Thomas clan" is a prestigious and aristocratic family that was only mentioned in Rise of Nightmares. The Thomas family also owns a holding company, the Thomas Foundation, funding specifically for scientific research. They adopted Viktor Fleischer after he had became orphaned at a young age and continued to fund for his educational studies. Viktor became a researcher working for the foundation and was eventually married to one of the Thomas family's member, Mary.

Though Viktor had became an independent researcher after leaving the foundation, the foundation continued to lavishly fund his studies, which were rumored to include superhuman abilities, rejuvenation, and eternal life, hinting that the family was well aware on the true nature of Viktor's research. After losing contact with Viktor, the foundation hired private investigator, Roland Childs, to locate Viktor.