σφῷν δ̓, dat. of interest, "for you two" (Ant. and Ism.), in your case. Some take it as partitive gen.: then it would mean, "of you two pairs," — the pair of brothers being one unit, and the pair of sisters another. But I know no parallel for such an use of a dual pronoun. It is different when “ἄμφω” is said of two "sides" or armies, considered as units ( Il. 2.123 “εἴπερ γάρ κ᾽ ἐθέλοιμεν Ἀχαιοί τε Τρῶές τε ι … ἀριθμηθήμεναι ἄμφω”): or when a dual verb has a twofold dual subject,
.“Ξάνθε τε καὶ σύ, Πόδαργε, καὶ Αἴθων Λάμπε τε δῖε
νῦν μοι τὴν κομιδὴν ἀποτίνετον
”
