It Was The Age Of Technology
The Steiner-Rohre family were very wealthy industrialists on Tera near the beginning of the Age of technology. They were firm believers that the stars were where the destiny of mankind lay and spent heavily, personal and through their companies, to advance their society into space.
With warp travel advanced to a usable level and the advancement of STC technology members of the Steiner-Rohre family asked for, and were given permission to emigrate into space. They were given command of a colony ship with an STC system including the Knight protector template. They went to the galactic east and set up an agricultural and mining world in a far system. It is believed that the families descendants again emigrated even farther at least once more but records are hard to find.
The Age of Strife
The Age of Strife cut off the settlement and, like most Knight Worlds, the local civilization fell back to and industrialized serfdom of sorts. The Steiner-Rohre family became rulers and protectors having used the STC system to create several Knights to protect the colony. With the loss of any united Teran control the local are of three or four cosines became self sufficient and thrived through these dark times.
The Great Crusade
As the Emperor brought the Imperium to the galaxy with his Great Crusade, many Knight worlds were brought back into the control of mankind. It was durning the Great Crusade the Forge World Triplex Phall found the Steiner-Rohre settlement and offered to allow them continued autonomy in exchange for allegiance to Triplex Phall. Triplex Phall took control of what remained of the STC and offered extended and renewed trading rules to the rest of human space. Triplex Phall and Steiner-Rohre worked together to hold off many xenos excursions in the area for many years.
The Horus Heresy
The Horus Heresy left Triplex Phall, and much of the Imperium under powered and unable to defend itself to the same levels as before the civil war. An Irk infestation took hold on the Steiner-Rohre home world and there was no longer enough firepower to force them back off planet. Well the Steiner-Rohre home world was going to be lost Triplex Phall took note of the dedication and devotion of this noble family and assisted in relocating the family and almost 500 retainers, along with all their Knights to the Minkar system, Giving them land and titles on Minkar III and giving Triplex Phall a reason to maintain a cohort of their own within the system. As this evacuation took place the Imperial Navy proceeded with an Exterminatus order for the planet.
Modern Times
The current head of the house hold is Barron Heinrich Leuthar Steiner-Rohre who presides from the keep build on the stony peaks of the Hawkesbury mountain range. The highland meadows allow the family to retain its agricultural heritage and the mineral rights on it lands keep them, and Triplex Phall, rich. A planetary lifting facility keeps their resources, and their Knights, in close range of the rest of the planet. Barron Heinrich has found it easy to align with Convent of Minkar, and through them is willing to work with Minkar Defense Forces but still remembers what the Imperial Navy did to they ancestral home and will only operate off world at the behest of Triplex Phall.