In Assassin's Creed Odyssey, Kassandra and Alexios are siblings.
Odyssey lets the player choose Kassandra or Alexios as the playable protagonist. The unchosen character becomes Deimos, a powerful figure whose role is central to the Cult of Kosmos and the game's family storyline. Regardless of the player's choice, the two characters are brother and sister.
Their family includes Myrrine and Nikolaos, and the story explores separation, betrayal, and attempts at reconciliation during the Peloponnesian War. Because either sibling can be selected as the protagonist, players sometimes describe Alexios as the default hero; the game officially presents both as selectable protagonists.
Assassin's Creed Odyssey is set in ancient Greece in the fifth century BCE. It is a role-playing game with dialogue choices, branching outcomes, and a large world covering locations associated with Athens, Sparta, and the Aegean Sea.