Upon seizing the thrones of Mycenae and Tiryns, Sthenelus also sent for Atreus and Thyestes, the sons of Pelops, and entrusted Midea to them.
Midea was celebrated as the residence of Electryon when he was the ruler of Mycenae and Tiryns, and it was the birthplace of his daughter Alcmene. It is the third major fortified city of the Argolid after Mycenae and Tiryns and was located roughly halfway between the two; it was built atop a conical hill and overlooks the
The Pelopids (children of Pelops) were related to the Perseids (children of Perseus) in several ways: first, they shared a common descent from daughters of Atlas — Sterope, the wife of Oenomaus and mother of Hippodamia, was a sister of Taygete and one of the Pleiades; Dione, the wife of Tantalus and mother of Pelops, was also a sister of Taygete, but she was one of the Hyades. Second, several of the sons of Perseus had married daughters of Pelops and Hippodamia — the tradition seems unconcerned here with the chronological discrepancy which would make these daughters the age of the Perseids' great-grandmother — Alcaeus married Astydamia, who was the mother of Amphitryon; Mestor married Lysidice; and Sthenelus married Nicippe. In sending for Atreus and Thyestes, then, Sthenelus was calling upon his brothers-in-law.
Electryon, by contrast, married his brother Alcaeus' daughter Anaxo, and Amphitryon, his nephew, married Alcmene, Electryon's daughter.