I know the voice
Early in Proteus, Stephen reflects on having been sired by "the man with my voice and my eyes." The thought anticipates a recollection, later in the chapter, of Kevin Egan saying to him, "You're your father's son. I know the voice." Egan's remark makes him symbolically a Nestor, like Deasy.
In the Odyssey, old Nestor remarks on young Telemachus' resemblance to Odysseus: "Your father? / Well, I must say I marvel at the sight of you: / your manner of speech couldn't be more like his; / one would say No; no boy could speak so well" (Fitzgerald 3.130-33). In Book 4, Menelaus and Helen also remark on how much Telemachus looks like Odysseus.
Stephen's relationship with Egan seems more congenial than the one with his employer, but he interprets Egan's Nestor-like comment as an effort to coopt Stephen to his revolutionary cause: "To yoke me as his yokefellow, our crimes our common cause. You're your father's son. I know the voice." As with Mulligan and Deasy, Stephen wants no part of such paternalistic guidance.