Answer: Stephen seems to have an uncomfortable relationship with his father. Stephen has developed a psychological distance from his father:
An abyss of fortune or of temperament sundered him [Stephen] from them [his father and his father's companions]. His mind . . . shone coldly on their strifes and happiness and regrets like a moon upon a younger earth.
Unlike his father, Stephen seems to be shy and reserved. Some aspects of Stephen's father's behavior, such as his drunkenness and his flirting with the barmaids, make Stephen feel humiliated.
He is embarrassed by his father's conversation with his companions, and he listens in awkward silence to their vulgar talk. Stephen's repetition of the lines from Shelley suggests that he is well-read, revealing another difference between Stephen and his father.