Kartir's own four rock inscriptions, the only sustained first person account of the early Sasanian priesthood to survive, describe his rise across the reigns of four kings from Ardashir I through Bahram II and his own religious offices and honors, but they are a career record, not a birth notice, and no outside chronicle supplies one either.
What would resolve this A Sasanian administrative or dynastic text naming Kartir's age or birth before his rise under Ardashir I, distinct from the career narrative his own inscriptions preserve.
OpenSasanian history, Zoroastrian religious historyMary Boyce, A History of Zoroastrianism