The pair profit from a bevy of injuries for coach Rudi Garcia’s side, who have a one-point lead over second-placed North Macedonia plus a game in hand and will qualify with a win over the Kazakhs in Astana on Saturday.
The group winners qualify directly for next year's World Cup in North America, with the runners‑up entering the playoffs.
"As everyone knows, there are quite a few injured players in the squad," Garcia told a press conference on Friday as he named the squad, “ but Vermant and Ngoy have both proven at their clubs that they are worthy of selection."
Belgium are without Kevin De Bruyne, Zeno Debast, Malick Fofana and record goalscorer Romelu Lukaku.
Vermant, 21, has started with Club Brugge in domestic competition and the Champions League, while 22-year-old Ngoy has made a successful transition to France’s Ligue 1 with Lille after playing at Standard Liege last season.
"Romeo brings a breath of fresh air, enthusiasm, and fighting spirit. Ngoy, in turn, has been a regular at Lille for some time. Both still have a lot to prove, but they can eventually become permanent fixtures,” the coach added.
Captain Youri Tielemans is back in the squad after injury, having made a comeback for Aston Villa on Thursday as a substitute in the Europa League.
He was named Belgium captain in September, but was forced to miss last month’s key qualifiers against North Macedonia and Wales. Midfielder Kevin De Bruyne took over the captaincy at the time but he is now injured, having had hamstring surgery.
After Saturday's trip to Kazakhstan, Belgium complete their campaign at home to Liechtenstein in Liege on Tuesday.
Squad:
Goalkeepers: Thibaut Courtois (Real Madrid), Senne Lammens (Manchester United), Matz Sels (Nottingham Forest), Maarten Vandevoort (RB Leipzig)
Defenders: Timothy Castagne (Fulham), Maxim De Cuyper (Brighton & Hove Albion), Koni De Winter (AC Milan), Brandon Mechele (Club Brugge), Thomas Meunier (Lille), Diego Moreira (Racing Strasbourg), Nathan Ngoy (Lille), Joaquin Seys (Club Brugge), Arthur Theate (Eintracht Frankfurt)
Midfielders: Amadou Onana (Aston Villa), Nicolas Raskin (Rangers), Youri Tielemans (Aston Villa), Hans Vanaken (Club Brugge), Charles Vanhoutte (Nice), Axel Witsel (Girona)
Forwards: Charles De Ketelaere (Atalanta), Jeremy Doku (Manchester City), Dodi Lukebakio (Benfica), Lois Openda (RB Leipzig), Alexis Saelemaekers (AC Milan), Leandro Trossard (Arsenal), Romeo Vermant (Club Brugge)
