The term Cousin was used by the Time Lords to designate "anyone of the same House", (PROSE: Lungbarrow, The Book of the War) although it was archaic by the time of the War in Heaven. (PROSE: The Book of the War)
Faction Paradox used the term for their most populous rank. Each Cousin had a rudimentary training in the Faction's techniques, and they received a shadow-weapon as part of their initiation into the rank. Most Cousins lived outside the Eleven-Day Empire tending to the Faction's interests and colonies in the rest of the universe. (PROSE: The Book of the War)