I would ask the question of Corney Keller, who can be found through his transcripts on eggsa.org or at his site kellercafe.nl .
According to "Personalia", Johann Greyling was from Linz in the Province of Saxony. He was married at the Cape to Johanna Lubbe and then to Jacomina Pelser. There is a reference to his will in the Stellenbosch Archive. Such wills often referred to places of origin and family members still in Europe.
As I said, in my case (Meintjes) the spelling of the progenitor's name varied wildly. It is only through the contemporary mention of his wife, Christina Bastiaansz and her family that one can be sure the various references are to him.