Please answer a question about the following article about Apollo:

It seems an oracular cult existed in Delphi from the Mycenaean ages. In historical times, the priests of Delphi were called Labryaden, "the double-axe men", which indicates Minoan origin. The double-axe, labrys, was the holy symbol of the Cretan labyrinth. The Homeric hymn adds that Apollo appeared as a dolphin and carried Cretan priests to Delphi, where they evidently transferred their religious practices. Apollo Delphinios was a sea-god especially worshiped in Crete and in the islands, and his name indicates his connection with Delphi and the holy serpent Delphyne ("womb").[citation needed] Apollo's sister Artemis, who was the Greek goddess of hunting, is identified with Britomartis (Diktynna), the Minoan "Mistress of the animals". In her earliest depictions she is accompanied by the "Mister of the animals", a male god of hunting who had the bow as his attribute. His original name is unknown, but it seems that he was absorbed by the more popular Apollo, who stood by the virgin "Mistress of the Animals", becoming her brother.

Who was Apollo's sister?
Artemis