M/M: Alexander and Bagoas: Athenaeus, Deipnosophistae XIII.lxxx

Please note that even though Bagoas was free and able to consent to Alexander's affection, many eunuchs were not so lucky, and spent the duration of their lives in slavery. It is important to ensure that we do not romanticize relationships that would not be considered consensual today, including the master / slave dynamic.  

In his book On Sacred Sacrifices at Troy, Dichaearchus states that Alexander the Great was so smitten by the eunuch Bagoas that he kissed him in the middle of a theater, and when the spectators applauded them, he kissed him again.

Dicaearchus certe, in libro De Solemni Sacrificio ad Ilium, ait, ita impotenter [Alexandrum] amasse eum Bagoam eunuchum, ut in totius theatri conspectu…eum suaviaretur: plaudentibus vero spectatoribus, & adclamantibus, paruit, iteruque retro eum osculatus est.

Δικαίαρχος γοῦν ἐν τῷ περὶ τῆς ἐν Ἰλίῳ Θυσίας [Ἀλέξανδρον] Βαγώου τοῦ εὐνούχου οὕτως αὐτόν φησιν ἡττᾶσθαι ὡς ἐν ὄψει θεάτρου ὅλου καταφιλεῖν αὐτὸν ἀνακλάσαντα, καὶ τῶν θεατῶν ἐπιφωνησάντων μετὰ κρότου οὐκ ἀπειθήσας πάλιν ἀνακλάσας ἐφίλησεν.

--Athenaeus, Deipnosophistae XIII.lxxx; Translated into Latin by Iohannes Schweighaeuser (1805)

Athenaeus was a scholar who lived in Naucratis (modern Egypt) during the reign of the Antonines. His fifteen volume work, the Deipnosophists, are invaluable for the amount of quotations they preserve of otherwise lost authors, including the poetry of Sappho.