Shakespeare's source for the subplot of Edmund, Edgar and Gloucester was a tale from Philip Sidney's Countess of Pembroke's Arcadia of a blind Paphlagonian king and his two sons, Leonatus and Plexirtus.

Following the death of Malcolm III from being stabbed in the eye,[citation needed] they ordered the killing of Edmund's half-brother Duncan II, the rightful heir, to take the Scottish throne.

Due to these clear parallels the choice of Edmund and Edgar as names may have been a nod by Shakespeare to the continued story of the Scottish throne following the events of Macbeth.

[a] Gloucester's younger, illegitimate son is an opportunistic, short-sighted character[1] whose ambitions lead him to form a union with Goneril and Regan.

But Edmund has some solid economic impetus for his actions, and he acts from a complexity of reasons, many of which are similar to those of Goneril and Regan.

Late in the play, Edmund begins to adhere to the traditional values of society, and tries to repent for his sins, but he crucially delays in rescinding his order to execute Lear and Cordelia.

[1] "Edmund, Son of Gloucester" by Chris Lambert was performed by Exiled theatre in 1996 and toured nationally.

The play studied Edmund's back-story from birth to his appearance in King Lear to explore the reasons for his actions.