In Homer, Helen and Menelaos have a single child, Hermione and there is a reference to Menelaos’ son Megapenthes. But there are no mentions of Helen having children with anyone else. The mythographical tradition fixes this.
Jacoby BNJ 758 F 6 = Scholia on Euripides, Andromache 898
“Lysimachus and some others report that Nikostratos was also born from Helen. But the one who gathered the Cypriot tales says that it was Pleisthenes who came to Cyprus with Aganos and that he was the child born to Alexander from Helen.”
Λυσίμαχος καὶ ἄλλοι τινὲς ἱστοροῦσιν γενέσθαι ἐξ ῾Ελένης καὶ Νικόστρατον. ὁ δὲ τὰς Κυπριακὰς ἰστορίας συντάξας Πλεισθένην φησί, μεθ᾽ οὗ εἰς Κύπρον ἀφῖχθαι καὶ τὸν ἐξ αὐτῆς τεχθέντα ᾽Αλεξάνδρωι ῎Αγανον.
“Menelaos fathered Hermione from Helen and according to some others Nikostraos; Akousilaos claims that [Menelaos] fathered Megapenthes with a servant girl who was Aitolian in race (she was named Pieres, or, it was Tereis who was Pierian; according to Eumelos he gave birth to a son named Xenodamos from a nymph named Knossia.”
Μενέλαος μὲν οὖν ἐξ ῾Ελένης ῾Ερμιόνην ἐγέννησε καὶ κατά τινας Νικόστρατον, ἐκ δούλης <δὲ> [Πιερίδος] γένος Αἰτωλίδος ἤ, καθάπερ ᾽Ακουσίλαός φησι, <Πιερίδος> [Τηρηίδος], Μεγαπένθη, ἐκ Κνωσσίας δὲ νύμφης κατὰ Εὐμηλον Ξενόδαμον.