The affix ñyaṅ comes in the sense of descendant after a word having vṛddhi in the first syllable and after a word ending in short i and after the words 1. kosala and 2. ajāda when they are the names of countries and kṣatriya-s.,
This debars अञ् ॥ Thus, to give example of Vriddha words, आम्बष्ठ्यः सौवीर्यः 'the sons or kings of Ambashtha and Sauvira'. Similarly to take words ending in short इ, we have आवन्त्यः and कौन्त्यः 'the son or kings of Avanti and Kunti'. These are words ending in short इ ॥ So also कौसल्यः and आजाद्यः, which are neither Vriddhas nor end in short इ ॥
Vart:- The affix 'dyan' comes after the word 'Pandu' when it is the name of a country as well as Kshatriya tribe. Thus पांड्यः, otherwise it will be पांडवः ॥ See 4.1.74.,