Fortun was the son of Sancho Iñiguez de Vizcaya but his mother is unknown. The date and place of his birth have not been found.
Fortun Sanchez
Sancho Iñiguez de Vizcaya (-c1070)
Íñigo López de Vizcaya
Lope III (V) Nuñez de Vizcaya
Usenda Ramirez y Godinez
Toda Hortiz de Nagera
Fortun Sanchez de Nagera