Exegesis:

euphranthēnai de kai charēnai edei ‘but we had to enjoy ourselves and to be glad,’ with hēmas ‘we’ (i.e. ‘we in the house’) understood; the clause refers to the inner compulsion which the coming home of the younger son caused. euphranthēnai refers to external celebration, charēnai to inner feeling.

ho adelphos sou houtos ‘your brother here,’ echoes ho huios sou houtos in v. 30, and implicitly criticizes the note of contempt in those words.

ezēsen ‘he began to live again,’ synonymous with anezēsen in v. 24.

apolōlōs ‘(he was) lost,’ with ēn understood.

Translation:

It was fitting to, or, “but we had to” (The Four Gospels – a New Translation, Good News Translation), ‘how would it have been possible not to,’ the personal pronoun to be taken as exclusive, where that distinction is obligatory.

Be glad, or, ‘rejoice,’ see 1.14.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.