The Prosperan Nobility is a caste of old families that continue to hold some sort of title or esteem amongst the politics of the Prosperan Trade Federation and the Republic. Maklia, despite being a monarchy, has solely the ruling family as nobility. The rest of the noble families of Maklia have either been absorbed by the ruling family or died off over time, and no new titles have been given in thousands of years.
The most notable and proliferated title a Prosperan noble holds is that of 'el', which falls on the end of a given name. It denotes membership in a Patrician family. In general, however, the style of name has grown to also be given to any number of people, and the state of having a name which ends in 'el' no longer automatically makes one a noble. Proof and paperwork is now required, though being a noble gives no particular benefits, except on Prospera where it entitles a family head to vote in the Federation elections. This title began as a way to distinguish the rich merchant families from other citizens of the federation. Certain forms of names also sound like 'el', but are not 'el', for instance 'Jibrail' or 'Mikhail'. Israfel and Izrael are both examples of members of Patrician families, though they both are no longer affiliated with their families.
In Traveller terms, a soc value of 12 or higher would justify holding a legitimate 'el' title. Some families will even induct a new member into their lineage, provided they have the coin.
Notable Patrician Families:
House Asher: House Asher (literally 'first' in ancient Prosperan) could be considered the oldest family in the Republic. Dating well back before even the Trade Federation was founded from Prospita, their power has waxed and waned in influence since time immemorial. Currently they are notable for owning the TAS.
House Blumenthal: Blumenthal is a foreign name. The House of Blumenthal is actually a Valentinian family, and has remained pureblooded for thousands of years. While by no means the richest of the families, a foreign family gaining so much prestige amongst Prosperan courts was an anomaly at the time, and to hold it is even stranger. Israfel was a notable member of Blumenthal. Currently, Blumenthal is a large trader of rare metals and colony materiel.
House Cohen: Cohen is a Prosperan family, and was the primary investor when the first colony ships were leaving to settle new worlds. These investments have, over a long period of time, paid out massive dividends, and Cohen can be considered one of the richest groups of Prosperans in the entire Republic. Cohen members are also the chairholders of the Rowen Trade Company.
House Khaye: Khaye is the most recently founded House. Khaye was founded after the Unification, by a family of rich entrepreneurs that wanted to be able to adorn themselves in titles officially. Mihr (styled 'Mihrel') is the most recent notable member of the Khaye family, though he does not wear the title.
House Reuben: Reuben is also a foreign name, and was the notable Maklian family which managed to find its way into Prosperan trade culture from centuries back. Izrael and Azazel are both notable members of the Reuben family. The Reuben family are primarily bankers.