Anthony Joshua has been sparring Marlo Moore, while Joseph Parker plans to use Tony Yoka in preparation for their unification fight.
America's Moore is a 1-0 prospect while Frenchman Yoka won the super-heavyweight gold medal at the 2016 Olympics four years after Joshua claimed the same prize.
The sparring partners have been drafted in to aid Joshua and Parker's sharpness before they collide on March 31 to unify their world heavyweight titles, live on Sky Sports Box Office.
"Yes, in two or three weeks to prepare him for his championship [fight] against Joshua," Yoka told Sky Sports News when asked about sparring Parker.
"Actually my team-mate in the gym, Marlo Moore, went to Joshua's training camp in Sheffield. I'm going to the other side."
America's Moore, 27, failed to qualify for Rio 2016 where Yoka, 25, won gold by notably beating Filip Hrgovic then Great Britain's Joe Joyce in the final.
Yoka is an inch taller than Joshua at 6'7'' and has an identical 82'' reach. He is 3-0 as a pro.
Yoka also owns a victory over Parker, who was representing New Zealand, in the 2010 Youth Olympic Games gold medal fight but will now join his former opponent's training camp in Las Vegas.
Both Moore and Yoka are based at trainer Virgil Hunter's California gym, which Amir Khan also uses.
Watch the Anthony Joshua vs Joseph Parker world heavyweight title unification fight, from Principality Stadium, Cardiff, on March 31, live and exclusive on Sky Sports Box Office.