A chance to talk about my NPCs? Woot! I wanted to go with a strong theme for each of my notable dynasties, which is why their circumstances are often incredibly contrived. I don't pretend that any of this is genius world building - it was more of an extended exercise in justifying nonstandard rogue traders and adding some surprise to the Expanse.
Kind of like FFG, I went with two staggeringly huge dynasties to rule the Expanse, each pretty much untouchable without powerful allies or a hell of a lot of powuh. The first was the Mode dynasty, whose thing was handing out letters of marque like they were candy, tying a number of smaller houses to themselves and utilizing their individual specialties for the betterment of house Mode. Counting the achievements of their sub-contractors as their own, they had a history of growing like a cancer and taking over more territory than any other house. It was ruled by lady Anastasia Mode and her retinue of the best and brightest from favoured dynasties, from her mobile luxury space station, The Benevolent Indifference. The players declined offers to join her on several occasions.
The second was the Golden Hand, a vast network of Mechanicus cultists supposedly led by a once tech-priest who was sent out into the Expanse during the earliest period of its discovery. The exact details of his identity - as well as the location of their main base - seems to be a mystery to everyone, but the Golden Hand has research stations and space docks in places most people don't even know exist, and act as an inofficial extension of the Adeptus Mechanicus inside the Expanse, repairing and maintaining technology at exhorbitant rates for those who don't want to take the time or the risk of going through the Maw. Many dynasties make use of their services, and hardly anyone knows exactly what kind of power they truly wield, but their reputation alone makes them one of the most powerful groups in Koronus. Ruled by [redacted] from the good ship [redacted, meme-virus released, have a good day].
But there's more. House Kulfi was a house of navigators with an Indian theme. Once in ancient history, their house had produced the Paternova, and the Paternoval Envoy had contrived for them to receive a Warrant basically just for the hell of it, in case they wanted to use it. They had fallen from grace somewhat since those days, but members of their family would still use the Warrant every few generations, traveling to rogue trader hotspots and increase their fortune through the sales of exclusive maps - and through the service of keeping those maps exclusive.
House von Scythus, headed by a Transubstantial Initiate (and Darth Vader expy) whose skill and fervor had accidentally gained him a cult of personality - the reason for his Warrant, as he was getting in the way of the local administration - represented the suicidally fanatic puritans of the Expanse. Hideously gifted in the area of brute force, they were poor in ambition and made few enemies, acting more like an easily redirected tidal wave than a shrewd opponent to be bested. Their ships included such notables as The First Stone, The Divine Ministration and The Latin Proverb.
To this day, I still don't know why I love talking about stuff I made up.