Apposition? Fab. Syrae XXXI

Fabulae Syrae XXXI - 2. Prometheus

Postquam deī omnia cētera animālia in mundō posuerant et etiam hominēs ex terrā ūmidā et mollī ignī mixtā confēcerant, Epimetheō (Dat.), Prometheī fratrī (Dat.), imperāvērunt ut singulīs animālibus mūnera daret.

I was wondering why fratrī was Dative. Are Epimetheō and fratrī in apposition?

Yes, “fratri” is an apposition and thus is in the same case as “Epimetheo”. This happens in all cases:

Epimetheus, Promethei frater, iussus est …
Dei Epimetheo, Promethei fratri, imperaverunt ut …
Dei Epimetheum, Promethei fratrem, iusserunt …

Gratias tibi ago.