Fiji will meet Australia and New Zealand in the World Cup group stage, making the loss of three potential players a significant setback.
Wests Tigers brothers Siona, Samuela and Latu Fainu are out of Fiji Bati's squad after failing to provide evidence of their Fijian heritage.
News Corp reported that the International Rugby League rejected their eligibility.
Fiji's 40-man preliminary squad, announced in early September, still features significant NRL and Super League talent.
Expected selections include Tigers teammates Apisai Koroisau, Sunia Turuva and Jahream Bula, alongside Viliame Kikau, Kurt Donoghue and Jacob Saifiti.
Manly's Brandon Wakeham and Caleb Navale, plus Super League players Maika Sivo, Taane Milne, Semi Valemei and Waqa Blake, are also expected to feature.
The brothers could instead pursue Tonga selection, though only Latu is likely to enter Kristian Woolf's discussions because Tonga has few half options beyond Isaiya Katoa.
Parramatta fullback Isaiah Iongi could partner Katoa, but his strongest position is fullback.
Latu offers stability in the halves and has filled in at hooker for the Tigers, giving Tonga a versatile option.
Another possibility is Junior Amone, who returned to professional rugby league earlier this year and has impressed in the QLD Cup.