Brightlord/Brightlady/Brightness are Alethkar titles/formalities for addressing a noble.
All Lighteyes are automatically nobles and outrank all Darkeyes. High ranking Darkeyes are permitted to marry low ranking Lighteyes but do not become nobles when they do.
There are a total of 22 known classes in Vorin society (10 noble, 10 non-noble, and 2 slave classes). In order, from highest to lowest ranking, they are: First through Tenth Dahn (Lighteyes), First through Tenth Nahn (Darkeyes), Parshmen, and Sas Nahn. It is possible for individuals and families to move up down within their respective grouping (Nahn/Dahn). Those who are declared to be Sas Nahn have glyphs branded on there foreheads permanently marking them as Sas Nahn. It is unknown whether a Lighteyes can become Sas Nahn or if there is a Sas Dahn equivalent for them.