“But they had no children.
Both were advanced
καὶ οὐκ ἦν αὐτοῖς τέκνον, καθότι ἦν ἡ Ἐλεισάβετ στεῖρα, καὶ ἀμφότεροι προβεβηκότες ἐν ταῖς ἡμέραις αὐτῶν ἦσαν.
Next Luke presents this unique portrait of Zechariah and Elizabeth, much like that of Abraham and Sarah in Genesis, chapters 18:1-15 and 21:1-7. They had no children (καὶ οὐκ ἦν αὐτοῖς τέκνον). Elizabeth was barren or sterile (καθότι ἦν ἡ Ἐλεισάβετ στεῖρα), often times a sign of God’s displeasure. They were both advanced (καὶ ἀμφότεροι προβεβηκότες) in their years (ἐν ταῖς ἡμέραις αὐτῶν ἦσαν). In other words, they were old folks, beyond child bearing years. Thus, only a miraculous birth would give them children.