E. Antipholus is the foil to S. Antipholus; he’s his twin’s mirror image, but he’s also the opposite of his brother in many ways. S. Antipholus constantly talks about his quest for identity, and he seems to carry a rather pensive air (with the melancholy that often attends it). E. Antipholus, by contrast, has set up what seems to be a full and fulfilling life for himself in Ephesus. He has a wife, maybe even a mistress, and all sorts of business associates. E. Antipholus is utterly settled in his life, and he doesn’t seem the kind of guy that would go traipsing about the world feeling incomplete without a family he never knew in the first place. E. Antipholus is the "normal guy" foil to S. Antipholus’s characteristic wanderlust for identity.
Adriana is balanced by her sister Luciana. Adriana’s most significant role is as E. Antipholus’s wife. As a married woman, her views on marriage are contrasted to the views of the unmarried Luciana. While Luciana takes the approach of believing women are wholly subservient to men, Adriana’s experiences as a wife have taught her that a more practical (and perhaps equal) arrangement is necessary in order to make a marriage work. Interestingly, Luciana admits that although she thinks she knows what a good wife should be like, she isn’t capable of it yet (which might reveal that her view is unrealistic). Adriana is evidence of marriage as a give-and-take arrangement, whereas Luciana would give up her freedom and be totally obedient.