Matthew 1:18

Footnote:

Greek μνηστευθείσης τῆς μητρὸς αὐτοῦ Μαρίας. Every one of these words is in the genitive case.

of she who is wooed
of the mother
of himself
of Mary/Bitter-Rebel

μνηστευθείσης "her who was wooed and won" is a participle noun in the genitive, aorist tense.

The phrase πρὶν ἢ συνελθεῖν αὐτοὺς is composed of the temporal particle πρὶν ἢ, meaning “before” or “prior to,” governing the aorist active infinitive συνελθεῖν (“to assemble together” or “to unite”), with the accusative pronoun αὐτοὺς (“them”) as its object. This construction denotes a temporal clause indicating an action occurring before the subject’s assembly or union. This construction or usage is rare, but not without purpose. The temporal aspect can lead a translator to render the infinitive as a past tense, e.g. "before they united" but this erases the infinitive-accusative sense. “Prior to uniting/assembling together themselves” is a more accurate and faithful rendering of πρὶν ἢ συνελθεῖν αὐτοὺς, because it preserves the infinitive’s non-finite aspect and does not impose a past tense finite verb. It captures the temporal sequence without transforming the phrase into a completed action.