What is the story of Aegisthus, Agamemnon, Clytemnestra, and Orestes? Why is it repeated so many times in The Odyssey?

Clytemnestra was unfaithful to her husband Agamemnon who
was in battle at Troy. Aegisthus was the apparent lover in the triangle who killed
Agamemnon in order to establish an intimate relationship with his wife. Orestes,
Agamemnon’s son, knew of how his father died but waited strategically until the
opportune time came, and avenged his father by killing Aegisthus and Clytemnestra, his
mother.

The story about Agamemnon, the infidelity of his
wife Clytemnestra with Aegisthus, Agamemnon’s death at the hands of the two lovers, and
the vengeance by his son Orestes on behalf of his father is repeated several times in
the story because:

• It is this story, and the
  courage of Orestes, that Athena employs to spur Telemachus into action regarding a
  similar situation facing his mother Penelope.


• The story
  is also used to strike a close resemblance between Agamemnon’s situation and his
  eventual death, with what Penelope is going through at the hands of unwanted
  suitors.


• The story is also used to show the difference
  between Clytemnestra and Penelope and also shows the benefits associated with fidelity
  and perseverance.


• At some point, Nestor shares the full
  story of Agamemnon’s death with Telemachus in order to improve his understanding of how
  such a thing could happen to a noble man, and the importance to decisively face the
  situation.