Lavinia is Ezra's wooden, stiff-shouldered, flat-chested, thin, and angular daughter. She is garbed in the black of mourning. Her militaristic bearing, a mark of her identification with her father, symbolizes her role as a functionary of the Mannon clan or, to use Christine's terms, as their sentry. Lavinia appears as the keeper of the family crypt and all its secrets, figuring as an agent of repression throughout the play. She will urge Orin in particular to forget the dead, compulsively insist upon the justice of their crimes, and keep the history of the family's past from coming to light. Lavinia's repressive stiffness and mask-like countenance mirrors that of the house, the monument of repression erected by her ancestors to conceal their disgraces. Ultimately this manor becomes her tomb, Lavinia condemning herself to live with the Mannon dead until she and all their secrets with her die.
Despite her loyalties to the Mannon line, Lavinia appears as her mother double from the outset of the play, sharing the same lustrous copper hair, violet eyes, and mask-like face. Christine is her rival. Lavinia considers herself robbed of all love at her mother's hands, Christine not only taking her father but her would-be lover as well. Thus she schemes to take Christine's place and become the wife of her father and mother of her brother. She does so upon her mother's death, reincarnating her in her own flesh.
In doing so, Lavinia comes to femininity and sexuality. Lavinia traces a classical Oedipal trajectory, in which the daughter, horrified by her castration, yearns to become the mother and bear a child by her father that would redeem her lack. Orin figures as this child as well as the husband she would leave to be with her son, that is, Peter substituting as Brant.
The Mannon son returned from war, Orin is the boyish counterpart to Aeschylus's Orestes. He loves his mother incestuously, yearning for pre-Oedipal plentitude, the mythic moment prior to the intervention of the father into the mother-son dyad. This pre-Oedipal paradise appears primarily in two fantasies: that of the secret world he shares with Christine in childhood and the Blessed Island he imagines as a haven from the war.
As the stage notes indicate, Orin bears a striking resemblance to the other Mannon men though he appears as a weakened, refined, and oversensitive version of each. These doubles are his rivals within the Mother-Son love affair that structures the trilogy, with Orin competing with Ezra and Brant for Christine's desire. Thus he flies into a jealous rage upon the discovery of her love affair that leads to Christine and Brant's deaths. Orin will then force he and his sister to judgment for their crimes in an attempt to rejoin his mother in death.
Christine is a striking woman of forty with a fine, voluptuous figure, flowing animal grace, and a mass of beautiful copper hair. Her pale face is also a life- like mask, a mask that represents both her duplicity and her almost super-human efforts at repression.
Having long abhorred her husband Ezra, Christine plots his murder with her lover Brant upon his return from the Civil War. She loves incestuously, repudiating her husband and clinging to her son as that which is all her own. She repeats this incestuous relation in her affair with Brant, rediscovering Orin in a substitute.
Like her double, Brant's mother Marie, Christine moves with an animal-like grace, grace that codes for her sexual excess. This grace makes her exotic, or even of another race, aligning her with the recurring figures of the island native. It makes sense that Lavinia must go among the natives to fully assume her figure.
As her characteristic green dress suggests, Christine is consumed with envy. She envies Brant's Island women, hating them for their sexual pleasures. Despite the desperate veneer of kindness, she envies Hazel for her youth, imagining her as a figure for what she once was. Before the threat of her oncoming age, she must secure her love affair with Brant at all costs.
As his homophonic name suggests, he is Agamemnon's counterpart, the great general returned from war to be murdered by his wife and her lover. We first encounter Ezra prior to his homecoming in the former of the ominous portrait hanging in his study. Here, as throughout the trilogy, Ezra is dressed in his judge's robes and appears as a symbol of the law.
Ezra's authority rests primarily in his symbolic form. Indeed, he is far more the figure for the law in this form than as a broken, bitter, ruined husband. Both before and after his death, Ezra will continuously appear in his symbolic capacities. His mannerisms, for example, suggest the unyielding statue-like poses of military heroes; to Christine, he imagines himself as a statue of a great man standing in a square. After his death, Lavinia will constantly invoke his name and voice. Christine will hear herself condemned by his corpse. Ezra's various images will call his family to judgment from beyond the grave.
Brant is a powerful, romantic sea captain. He has swarthy complexion, sensual mouth, and long, coal-black hair. He dresses, as if some romantic Byronic ideal, in almost foppish extravagance with touches of studied carelessness. The child of the illegitimate Mannon line, he returns to wreak vengeance on Ezra's household. He steals Ezra's wife and seduces Lavinia to conceal their affair. Brant also of course bares a striking resemblance to the other Mannon men. He does so as yet another son incestuously enthralled with Mother and her substitutes.
In Mourning Becomes Electra you write: "Oedipus was the Theban king who unwittingly killed his father and MURDERED his mother." [Emphasis mine].
It should read: "Oedipus...MARRIED his mother!"
(Oedipus' mother Jocasta did commit suicide after learning her lover was her son. Oedipus however did NOT "murder" her.)