Mursili II's own Annals and Plague Prayers fix his father Suppiluliuma I's reign and his own accession after two elder claimants died of plague, but nothing independent of that political record gives a birth year for Mursili himself.
What would resolve this A Hittite administrative or dynastic text naming Mursili II's age at accession or his birth year, distinct from the Annals' political narrative of the succession crisis.
OpenHittite history, Late Bronze Age Anatolian chronologyItamar Singer; Harry A. Hoffner Jr. (ed.), Hittite Prayers