Besides the emplyment of the fossilised ὁ μέν ... ὁ δέ ... etc structural markers, is this τοῦ in the quotation of Aratus the only NT example of ὁ employed as a relative?Acts 17:28 (part) wrote:Τοῦ γὰρ καὶ γένος ἐσμέν.
As the opening lines of one of the most widely read (and perhaps studied and recited), copied and translated verse works of antiquity, it is likely that it would have been recognised in situ by educated readers as a text employing the epic relative, rather than following the Attic / Koine habit of using αὐτός. Here are the opening few lines of the Phaenomena with the examples of the relative pronominally used ὁ emboldened and encolorated.
Aratus, Phaenomena, 1-7a wrote: ἐκ Διὸς ἀρχώμεσθα, τὸν οὐδέποτ᾽ ἄνδρες ἐῶμεν
ἄρρητον: μεσταὶ δέ Διὸς πᾶσαι μὲν ἀγυιαί,
πᾶσαι δ᾽ ἀνθρώπων ἀγοραί, μεστὴ δὲ θάλασσα
καὶ λιμένες: πάντη δὲ Διὸς κεχρήμεθα πάντες.
τοῦ γάρ καὶ γένος εἰμέν: ὁ δ᾽ ἤπιος ἀνθρώποισιν 5
δεξιὰ σημαίνει, λαοὺς δ᾽ ἐπὶ ἔργον ἐγείρει,
On τοῦ surviving redaction during the transmission process or being misquoted and εἰμέν being standardised to ἐσμέν at some point of time, there are a number of possible hypotheses that might explain that, from popularist quotations, or various paths to conformity to the style of the NT's genre.Phaenomena, translated by G. R. Mair, Loeb, 1921 wrote: From Zeus let us begin; him do we mortals never leave unnamed; full of Zeus are all the streets and all the market-places of men; full is the sea and the havens thereof; always we all have need of Zeus. For we are also his offspring; and he in his kindness unto men giveth favourable signs and wakeneth the people to work, reminding them of livelihood.