Marquess Madness

Second in aristocratic rank to a duke is a marquess (occasionally marquis), and often the oldest son of a duke is known as the Marquess of Something because that's one of his father's lesser titles. But a marquess can also hold the title in his own right; in history when earls have provided great service to the sovereign they're often rewarded with a higher title -- sometimes they're made a marquess, and sometimes they're jumped all the way up to being a duke.

The wife of a Marquess is a Marchioness. Their eldest son uses one of his father's lesser titles as a courtesy, so the son of a marquess is sometimes an earl -- but one without personal power.

A Marquess is addressed as My Lord, or Your Lordship, and if he's the Marquess of Sheridan he's referred to as Lord Sheridan.

The younger sons of a marquess are -- like the sons of dukes -- known as Lord Firstname Lastname, and all the daughters of a marquess are Lady Firstname Lastname. They can be referred to in person as Lord Firstname or Lady Firstname.