Although rarely seen, in Royal Imperious, some Knight Chapters take hold in our military, they are called Space Marines. They are the Deathwatch, Grey Knights, Lamenters, Ultramarines, and the Imperial Fists.
Deathwatch, Chapter I, Vyrakk
Grey Knights, Chapter II, Vexicaus
Lamenters, Chapter III, Astrayas
Ultramarines, Chpater III, Vyrakk
Imperial Fists, Chapter IV, Vannadin
Together, these chapters make up the Adeptus Astartes, and the Grey Knights and Deathwatch make up the Sanctus equites Inquisitionis. They fight for honor, duty, and the glory of The God Emperor. Only Sactus equites Inquisitionis knights are referred to as "Sir" or "Madame"