Have we already seen some people of the former crew of Gold Roger?
At least Claucus( the doctor who helps the giant whale) seems to know Roger. Cause when the straw-hats leave, he says:
"Maybe they are the pirates we have been waiting for... Don't you think so , Roger?"
Claucus is 71, perhaps he the Pirate king's crew former doctor.
Dragon, who says something similiar could also be... or doctor Kureha... who knows?