Designed for the original Camelot Cosmos game, which takes Arthurian knights to the stars using the FATE system, this resource - being pure background with little in the way of game mechanics - could easily be repurposed to provide a detailed background, replete with interrelationships and rivalrys, for the nobility in any game. Not just fantasy either, for example Traveller makes heavy use of nobility within governmet - the Rule of Man - yet apart from a few notables, little is said about them.
What this work does is present groups of noble families, showing how they interact with each other. Presuming a feudal system where certain familys hold sway over others, and in turn are responsible for their wellbeing and protection, each member house of every group is given a short write up that explains their characteristics. For example, House Proudham, vassals of House Sweetwater, are said to outdo even their overlords in piety and have an excellent relationship with the Church. They represent the Sweetwaters when negotiations with the Church take place, and many members of the family serve as priests, often becoming household confessors to other houses under Sweetwater jurisdiction.
Each house also has a brief description of their family armourial bearings, motto, the basis on which the family wealth is based, their general attitude, strengths and weaknesses and a defining characteristic - perhaps a physical feature or a favoured profession - of family members.
It makes for a fascinating read and whichever ruleset you choose to use it with will make the nobility - and their intrigues - blossom into a rich and complex tapestry within your game. It may be background politics, doing no more than providing the odd bit of work or patronage for your characters, or they may be heavily involved in the continuous dance of seeking power and influence, but however you use it the shared alternate reality of your game will be enhanced.