Tisamenos, King of Argos, Mycenae and Sparta

Tisamenus or Tissamenus (Greek: Τισαμενός), in Greek mythology, was a son of Orestes and Hermione, who were first cousins twice over (their mothers were sisters and their fathers were brothers), so Tisamenus had only four great-grandparents, instead of the usual eight. Tisamenus succeeded his father to the thrones of Argos, Mycenae and Sparta and was later killed in the final battle with the Heracleidae. The latter were led by Aristodemus, Cresphontes, Oxylus, Temenus and sought to retake the Peloponnese as their ancestral land. Following his death the victors divided his lands among them. Cresphontes became King of Messene, Oxylus of Elis and Temenus of Argos. Aristodemus was killed during the final battle but his twin sons Eurysthenes and Procles jointly received the throne of Sparta. The historical Kings of Sparta belonged to the co-ruling houses of Agidae and Eyripontae and claimed their respective descent from the brothers.

• https://en.wikipedia.org/wiki/Tisamenus_(son_of_Orestes)