Vieillir belong to the 2nd
group. Vieillir is a common french verb.
Vieillir is conjugated the same way that verbs that end in : -ir
Vieillir is conjugated with the two auxiliaries être
Vieillir verb is
direct transitive, intransitive.
French verb vieillir can be conjugated in the reflexive form: Se vieillir
verb is a direct transitive verb, so passive voice can be used.
Attention: passive voice can only be used when vieillir verb is conjugated with auxiliary avoir.