I have been building my own world for an ongoing campaign in hopes that my players want to try some of the third party content created by Matt Colville, Strongholds and Followers.  In that content the players have a framework of guides/rules for building a stronghold, which in many cases would become the seat of power for a Baron, or later an even more influential noble.  But for all that to make sense, there needs to be NPC nobles in the setting.  So a big part of the construction of my setting is describing the realm and the nobles that are running it.  From that, you also get the connection between being a Lord and having responsibility to manage some land.  The S&F Content allows you to leave those details to a Follower, but it an important element that ties it together.

The Party has a paladin in it, and a fighter.  If building a castle isn't your thing, Matt has other strongholds sketched up for other character types.  The main groups are Keep, Wizard's Tower, Cleric's Chapel, or an Establishment.  The Keep is intended for the Noble Lords as their seat of power over some range of land.  There are also Barbarian Camps, Ranger's Lodge, or a Pirate Ship.  Under the Wizards Tower, there are variations for a Sorcerer's place to commune with their patron, a Druid's Grove and stuff like that.  The Chapel can be for a Cleric as easily as it can be for a Paladin, and can grow into a Cathedral.  The Establishment can be any kind of business or a mixture of them, typically a Tavern for Rogues or a Theatre for Bards.

So on the following pages I plan to share my structure for the nobility of a kingdom called Calanthi.  The Kingdom was settled on the shore of a great lake hundreds of years ago by four noble families.  Most recently, after some long thought, the current King decided he would call for an Annexation of land to the north to expand the kingdom for another ten generations.  Three expeditions went north, about ten years apart and conquered a like sized region so that now the kingdom has double the area it had before.  The land was used by Orcs that practiced a nomadic lifestyle following herds as hunter-gatherers.

Now thirty-five years after the beginning of The Great Annexation (as called by the nobles, and The Orc Wars by the common people) the Kingdom wants to establish formal relations with the Orcs in hopes that they can agree on a permanent boundary between their cultures.

I think that warlocks commune with patrons more than sorcerers that may or may not know where their magic comes from, but the concept is otherwise good. Probably only for rich adventurers, so will come into play later on rather than at the start

Yes, in the book Matt fleshes out a few of these things pointing out that if we were to use a straight up DMG progression, the party might be in a position to build a stronghold by level 7, but probably later.  The cheapest stronghold, an Establishment, costs 6000gp to build at level 1 and the Keep costs 10,000gp.

The kingdom of Calanthi was founded when a group of wealthy noblemen financed an expedition north across the great sea.  They were looking for a fabled Elven City or Ruin, they knew not which, on the northern coast.  What they did find was a ruin of a stone city at the mouth of a river.  They sent an expedition ashore and that expedition was never heard from again.  They sent a second expedition who found stone remains of an explorer from the first expedition, pierced with an arrow.  The second expedition went a bit further and killed two Medusai before withdrawing to their boats and back to the ships.  The expedition went and sent another party ashore on the opposite bank.  This became the supply base for the expedition.

Additional explorer parties were sent ashore and eventually mapped out an area about 100 miles inland and stretching over 200 miles along the coast.  They found plenty of resources; good farmland, timber, herds, game.  The leaders decided to found settlements which became Calanthi, the Great Nation on the Lake.  The four families that funded the expedition became the Lords of the new nation.

There were two rivers about 30 miles apart at the coast that moved further apart as they went inland.  Between the rivers the King established "The Ruling Province", which later became known The Original Province.  Beyond the river to the west he established the Primary Duchy, and beyond the river to the east the Second Duchy.  The king ruled from the capitol about 50-60 miles inland on the bank of the west river, which became known as the Chrystahl River.  His oldest son, the Prince, ruled the west duchy from a city further inland on the Chrystahl River.  The king's second son ruled the east duchy from a city on the bank of the other river to the east known later as the Green River.  The king's three close friends that help fund and organize the expedition were elevated in this new kingdom from the rank of Marquis to Grand Marquis.  As a Grand Marquis they were "preferred" over other marquis in the kingdom.  One Grand Marquis became the Watchman of the Western Duchy and appointed a nobleman to serve as the chief military advisor, a Marshal, and the Grand Marquis was a trusted advisor to the King's son, the Prince.  Another Grand Marquis became the Watchman of the East Duchy and appointed a Marshal over The Armies of the East.  The third Grand Marquis remained in the Original Province as an advisor to the King, and he likewise appointed a Marshal over The Armies of the North.

Other nobles that supported the expedition were rewarded with titles and land in the New World as it was then spoken about.  In all, the kingdom had a King, a Prince, a Duke, three Grand Marquis, Ten Marquis, Four Counts, Three Earls, one hundred Barons, and eighteen Grand Barons when everything was "settled".  The Marquis were appointed over counties on the frontier border of the kingdom.  They enjoyed stature over the Counts and Earls that also presided over counties because on the frontier they had special responsibilities to the realm.  Counts were also appointed over counties, but were not on the frontier.  All these positions included the right of hereditary title, so that the first son of a Marquis would become a Baron, and then elevated to be a Marquis upon his father's passing.  The same hereditary title existed for the Count and his son.  But the title of Earl did not include hereditary title because it was reserved for an Arch Bishop of a Duchy.  The Earl presided over a county, but the title passed to the next Arch Bishop, not to the Arch Bishop's son.

Each County contained five baronies.  One barony was reserved for the oldest son of the Marquis or Count, that upon reaching the age of twenty five, he would be seated as the Baron in advance of becoming the Marquis or Count later.  One barony was reserved for the Bishop of the County, and like the Earl, this position carried no hereditary title, because the title passed to the next Bishop of the County.  This left three other baronies per County to appoint barons for service to the King.  On paper, these appointments were the purview of the Dukes and Marquis, but in practice the King appointed every Titled Nobleman in the kingdom for service to the king during the exploration and subsequent campaign to subdue the wilderness. 

Some special conditions existed for the daughters of the top nobles of the kingdom.  It was, by law, the king's right to agree to the marriage of every princess in the kingdom.  If the princess and her family couldn't find something suitable for her station, the king would have a princess married to a nobleman of his choice (with close consultation with the princess' father) and then the new groom would be appointed a Grand Baron and given an affluent town to govern.  Barons presided over some 400 square miles of farmland, cities, towns, villages and hamlets.  A Grand Baron presided over one affluent town.  But the princess would continue to live in luxury and the Grand Baron would be given responsibilities in the court assisting the Marquis.  The position of Grand Baron did not convey hereditary title either.

A Baron presides over about 360 - 400 sq miles of land (230,000 - 260,000 acres).  He can not manage this much land by himself so he appoints other nobles, those without titles, to preside over smaller areas called Manors, and these nobleman are called Manor Lords.  Manor Lords hold prestige because they are "landed nobles" as opposed to "unlanded nobles", who are children of nobles who have never secured a position that carries a land grant.  Many knights are unlanded nobles, but being a noble is still better than not being a noble.

A Manor Lord owes duties and service to his baron.  The duties are typically a number of bushels of grain that must be given to the baron each year.  The baron also has the right to buy any additional grains produced on the manor at the accepted price.  The baron maintains control over the grain mill and he has his miller grind the grain into flour.  Then the Baron can sell the flour back to the Manor Lords and use the money for other things so his "assets" are not all tied up in bags of grain.  The service is a variation on serving in the army, except Manor Lords had to perform service as knights.  Some manor lords were older and they paid other unlanded knights to perform their service for them.  Some manor lords were not trained knights and likewise paid knights to serve in their stead.  But many manor lords would ride off and perform their service training with the army or even going on campaign.  Barons and higher nobles were not allowed to buy their service from others.  They had to perform their service in person.  For this reason, most sons were trained to become knights so they would be able to perform their service and not cause their Charter to come under review by the nobles.

Manors could be as small as 600 acres, but were typically larger up to 6000 acres.  The number of farmers employed on the farm was increased in proportion to the size because the Baron expected a duty per acre; more acres = more duties.  But, smaller land grants were given to nobles that performed other services, and these were called estates.  The granting of an estate gave the owner the means to earn their own living but they typically had a primary job to do that granted them an estate.  For example, the Baron's Chamberlain would have an estate immediately outside the town/city where the baron presided.  The Chamberlain performed his job for the baron but hired a foreman to manage his estate, which derived an income for the Chamberlain.  The High Sheriff, the Treasurer, the Captain of the Guard and a few other officials would have an estate instead of being paid for their services.  Nobles that ran estates were landed nobles.  They did not owe service to the king for their estate.  They owed it to the baron (or Count, or Earl, or Marquis, or Duke).

Beneath manor lords were freemen farmers, men of responsibility that were able farmers.  A freeman farmer would allow other tenant farmers to come farm plots within his farm.  The farmer would provide a barn and animals to give the tenants the means to do their work, and he might provide other amenities.  But the tenant farmers had to produce or they could be kicked off the land.  Being a tenant farmer was generally better than many other occupations, so farmers worked hard to maintain their positions.

Some farmers lived in small settlements and walked out to their fields from a hamlet each day.  As a result, their farms were usually smaller than farms found on a manor.  A hamlet was the smallest settlement size, unless you count manors or a cluster of four farm houses as a settlement.  A hamlet would have a barn to store grains, feed, tools and animals for work.  A hamlet would have a blacksmith that was able to maintain tools or make the simplest things like an axe.  A hamlet might have a monk that lived within the settlement, and a hamlet would be visited by a clergyman and a sheriff on a routine basis.  Hamlets were administered on paper by the baron's sheriffs, and a reeve would be elected or appointed to handle minor things, but the nearest manor lord often was the real power over a hamlet.  It was common for there to be about one hamlet for each manor.  Woodsmen, hunters, herders and some craftsmen lived in hamlets too.  Herders were pretty simple to manage.  They had a herd of a specific size and they managed their herd.  Woodsmen were given an allotment of trees they could take.  The Sheriffs were responsible to keep track of this.  Likewise, hunters were given specific quotas of game they could take and the sheriffs had to keep track of that also.  If a hunter killed an extra turkey or deer that could be smoothed over by transferring the kill to another hunter that wasn't reaching his quota.  But if they began to exceed their quota and were declared poachers, there would be dire consequences.  A number of teamsters were also residents in the hamlet.  They would spend many days dragging trees out of the forest and then hauling them to a mill.  During harvest they would carry wagons and wagons of grain to the mills, and then carry more periodically all year around.