Declension table of ?vayasyatva

Neuter	Singular	Dual	Plural
Nominative	vayasyatvam	vayasyatve	vayasyatvāni
Vocative	vayasyatva	vayasyatve	vayasyatvāni
Accusative	vayasyatvam	vayasyatve	vayasyatvāni
Instrumental	vayasyatvena	vayasyatvābhyām	vayasyatvaiḥ
Dative	vayasyatvāya	vayasyatvābhyām	vayasyatvebhyaḥ
Ablative	vayasyatvāt	vayasyatvābhyām	vayasyatvebhyaḥ
Genitive	vayasyatvasya	vayasyatvayoḥ	vayasyatvānām
Locative	vayasyatve	vayasyatvayoḥ	vayasyatveṣu

Compound vayasyatva -

Adverb -vayasyatvam -vayasyatvāt