The Nightrays were all of the headhunter victims throught out the series. There are however many others who was also killed by the headhunter as well.
The first victims were Fred Nightray and Duchess Nightray's brother. The second victims were Ernest and Claude Nightray. The third victims were Vanessa Nightray and her servant Hans. The final victims were Duke Nightray and Elliot Nightray who sacificed himself in order to stop the beheading.
There were also many other victims that were not of the Nightray. There were some guests who were invited to Yura's mansion killed by the Humpty Dumpty copies. Master Rytas, Marie, and Gruda were also victims of the headhunter.