In Assassin's Creed Odyssey, Alexios is revealed as Kassandra's sibling. The game presents Alexios as Deimos, a powerful and dangerous figure connected to the Cult of Kosmos.
Odyssey lets the player choose either Kassandra or Alexios as the main playable character at the beginning. The unchosen sibling becomes Deimos in the game's principal narrative, which means the answer depends on the question's specified protagonist. With Kassandra selected, Alexios fills that role.
Nikolaos is the siblings' adoptive father, while Stentor is associated with their family and the Spartan military. Brasidas is a historical Spartan commander who appears as an ally. These relationships can be confusing because Odyssey combines family drama with real historical figures and a branching story structure.