- "Under my brother behalf, Gideon Borgia will become an Assassin in the French Brotherhood of Assassins!"
- ―Joseph introducing Gideon Borgia to the Assassin Order, 1844
Joseph Dorian (1802-1889) was Master Assassin and Mentor of the French Brotherhood of Assassin. Hoping to live up to his father legacy, Joseph became a Assassin and eventually becoming Master Assassin at the age of 20 and then becoming Mentor in his later ages. He was the second son of Arno Dorian and Lucile Kenway, and the younger twin brother of James Dorian and the younger brother of Adélaïde Dorian. He is also the uncle of Caroline Dorian and the adopted uncle of Gideon Borgia, and also the husband of Master Assassin Catherine Forester and also the uncle of Antoinette Dorian and the grand-uncle of Ethan Arno Frye.