Eurysthenes in the context of "Agiad dynasty"

For most of its history, the ancient Greek city-state of Sparta in the Peloponnese was ruled by kings. Sparta was unusual among the Greek city-states in that it maintained its kingship past the Archaic age. It was even more unusual in that it had two kings simultaneously, who were called the archagetai, coming from two separate lines. According to tradition, the two lines, the Agiads (Ἀγιάδαι, Agiadai) and Eurypontids (Εὐρυποντίδαι, Eurypontidai), were respectively descended from the twins Eurysthenes and Procles, the descendants of Heracles, who supposedly conquered Sparta two generations after the Trojan War. The dynasties themselves, however, were named after the twins' grandsons, the kings Agis I and Eurypon, respectively. The Agiad line was regarded as being senior to the Eurypontid line.

Although there are lists of earlier purported kings of Sparta, there is little evidence for the existence of any before the mid-sixth century BC.

In Greek legends, Procles (Greek: Προκλῆς, "the renowned") was one of the Heracleidae, a great-great-great-grandson of Heracles, and a son of Aristodemus and Argia. His twin was Eurysthenes. Together they received the land of Lacedaemon after Cresphontes, Temenus and Aristodemus defeated Tisamenus, the last Achaean king of the Peloponnesus. Procles married Anaxandra, daughter of Thersander, King of Kleonoe, sister of his sister-in-law Lathria, and was the father of Soos and the grandfather of Eurypon, founder of the Eurypontid dynasty of the Kings of Sparta.

The title of archēgetēs, "founding magistrate," was explicitly denied to Eurysthenes and Procles by the later Spartan government on the grounds that they were not founders of a state, but were maintained in their offices by parties of foreigners. Instead the honor was granted to their son and grandson, for which reason the two lines were called the Agiads and the Eurypontids.

The Return of the Heracleidae is an ancient Greek myth concerning the return of the descendants of the hero Heracles to the Peloponnese, Heracles's homeland, and their conquest of various realms in the region. In the myth, Heracles was assisted by the Dorians: the story served as an aetiological myth for the Dorian communities of the Peloponnese, particularly Sparta.

According to the myth, Heracles's children (the Heracleidae) were forced from the Peloponnese by Eurystheus, and settled in the northern Greek region of Thessaly, where Hyllus, Heracles's eldest son, formed an allegiance with the Dorians. The Heracleidae killed Eurystheus, with Athenian support and protection, but Hyllus's attempt to retake the Peloponnese ended in failure and his own death in battle. Following the advice of the Oracle of Delphi, Hyllus's great-grandson, Temenos, led his relatives in a successful invasion, fifty years later, with the help of the Dorians and Oxylus. Temenos then divided the kingdoms of the Peloponnese between himself (receiving Argos), his brother Cresphontes (who received Messenia), and Eurysthenes and Procles, the sons of his brother Aristodemus, who had been killed before the Heracleidae reached the Peloponnese. Eurysthenes and Procles jointly received the kingdom of Sparta, founding the city's dual royal lineage.