A lineage is a direct descendancy of retired and new characters as chosen by the player. If you created two characters and are playing them together in one session or alternating them between sessions, they each have their own lineage. When one retires, the next character you start can either be their own new lineage or part of the one that retires, your choice. If you want the perk, you'll want to make it part of the lineage of a retired character.