In Assassin's Creed Origins, which Medjay from Siwa becomes an Assassin founder?

Bayek of Siwa is the Medjay from Siwa who becomes a founder of the Assassin Brotherhood in Assassin's Creed Origins.

Bayek is the game's principal protagonist and a protector of the Siwa region in Ptolemaic Egypt. His investigation begins after a personal tragedy and draws him into a conspiracy involving the Order of the Ancients, the organization that precedes the later Templar Order.

Bayek and Aya establish the Hidden Ones, the organization that develops into the Assassin Brotherhood. Their early creed and methods explain why later Assassins operate from secrecy and oppose the Templars. The game therefore functions as an origin story for the franchise's central organization.

Aya is Bayek's wife and a major historical character, but she is not the answer to this question. Senu is Bayek's eagle companion, while Hepzefa is a friend from Siwa. Origins was released in 2017 and introduced a more role-playing-focused structure.