Clearly, there are more characters in these three plays individually and together than in Prometheus Bound, and the ethos of individual characters is maintained so that their character is consistent through the three plays. This differs from what might be seen in the three plays by Sophocles about Oedipus, but Oedipus Rex, Oedipus at Colonus, and Antigone were not linked and were indeed each part of different trilogies of plays on the same basic subject. In the Oresteia, characters carry from one play...

The trilogy gains its name from the central role of Orestes, and there is unity of plot in that each of the plays centers on the travails of Orestes and the pursuit of him for killing his mother and because Agamemnon killed his daughter. The unities of time and place are maintained within each play, though the three plays take place in different locales and altogether cover more than one day.
Works Cited

Aeschylus. Oresteia (Richard Lattimore, tr.). Chicago: University of Chicago Press, 1953.

Aeschylus. "Prometheus Bound." In Greek Tragedies Volume I, David Grene and Richard Lattimore (eds). Chicago: University of Chicago Press, 1960.

Aristotle. The Complete Works of Aristotle: Volume Two (Jonathan Barnes [ed.]). Princeton: Princeton University Press, 1984.