Well, I did not invent these words (егоный, еёшний, etc.). In any case, in the Slavic languages there is a long lasting tendency to make the possessive pronouns of the 3rd person declinable.No, this is not standard Russian.
In Russian these are not declinable, it is always его, её, их (his, her, their)
It's not used in poetry, especially "high-level poetry" (whatever it means).It is strange for me that the pronouns "ихний" (их), "евоный" (его), "ейный" are
low level мужик spoken words --- but used in high level poetry.