Also called the "Azure Empire" by the Thaurans themselves.
During the early history of United Earth (before Earth became part of the United Stars), colonization was greatly encouraged and heavily sponsored by the government.
One of these groups were a group of mostly French (but also Belgian, Flemish, Dutch and eventually even joined by a group of Sarans). 
This group lamented the loss of national sovereignty and the loss and disregard of the concept of true nobility. Their leader, a man named René Thauran, born in the French city of Rouen, he openly lamented the loss of true French identity; of French culture and values.
He managed to gather a sizeable group of about 30,000 that agreed with him. Hew claimed to be of olf French noble heritage and kinship to French Kings.
Unfortunately documents and evidence of this has been lost in time, but his claim and ideas resonated especially with Europeans who considered the influence of American values in the new World government as too overwhelming and oppressive. They rejected the ideas of Pan Saran and Saran that influenced Earth development after the Ascent.
When Rene Thauran and his group were offered a world of their own, they agreed to leave Earth (As part of the Second Exodus )
As part of their Genetic Alteration package, the Thaurans requested to be distinctly different from other Earthers and wanted "Blue Blood ". (At least that is what the partial and incomplete documents of that time say) That the idea resulted in Blue skin rather than Blue Blood is a fact that is not well documented. It is not known it was an accident or on purpose.
However the Thaurans as the colonists called themselves, embraced the result and further deepened the results with additional genetic alterations and selected breeding.
A group of Sarans who agreed with the Thauran ideas, that nobility was not just a form of social development, but a state of mind. A core philosophy and a defining aspect of man's true nature joined the Thaurans. Adding Saran technology and resources to the group.
The Thauran group (45,120) left the Sol System in 2148 and arrived with all three arks at Normandie, planet in 2151. The conditions at Normandie planet were not at all as the Colonist bureau promised them to be.
The Saran members of the group, knew of a world that was much better suited and the decision was made to move there.
A miscalculated Hyper-Jump however sent the three Arks on an odyssey and into the then completrly un-explored and unreachable Spinward sector of the M-0 galaxy.
Finally the group found a suitable and apparently uninhabited gardenworld (Le Havre Bleu ).
The Colony thrived without any contact to the Union and spread over eleven star systems and seventeen planets. ( today includes over thirty star systems and over a hundred planets.)
The Thauran colonists developed their own culture, technology and adopted their own brand of a hereditary noble system. Each of the Thauran planets is ruled by a king, and they are in turn answer to the emperor.
Contact with the United Stars of the galaxy was reestablished 1600 years ago and the Thauran Empire opted to stay independent until the Y'All Invasion. Facing the seemingly unstoppable invaders from another galaxy, the Thauran Empire joined the United Stars.
The local laws and government stayed as it was and little has changed for the average Thauran citizen.
Thauran lore took the notion of being of Blue blood quite literally and used genetic manipulation from early on to create blue skin, today almost all Thauran feature blue skin in various shades.
The Thauran representative is not elected but appointed by the Emperor.
Intricate and complicated internal politics among the noble houses is still the core of everything Thauran.
According to legend, the Blessed Blue Virgin appeared to Rene and helped him find the new planet.
 French, Belgian and Dutch are nationalities, from respectively France, Belgium and the Netherlands.
Flemish and Walloons are cultural ethnicities using respectively Flemish Dutch and French (walloon, a french dialect, is almost defunct now in 2019).