Baronets and their ladies

Bridging the gap between the peerage (dukes, marquesses, earls, viscounts, and barons, along with their families) and commoners (pretty much everybody else) are the baronets.

Like a knight, a baronet is addressed as Sir Firstname Lastname, or more familiarly, Sir Firstname. (He is not called Sir Lastname, and never Lord Lastname). His wife is referred to as Lady Lastname.

Unlike a knighthood, a baronetcy is hereditary, with the eldest son succeeding to the title upon the death of his father. At that time, if the new baronet is married, his wife becomes Lady Lastname, while his mother's form of address changes to Firstname, Lady Lastname.

A very few modern day baronetcies have been created for women, and a small handful of baronetcies can be inherited by women or through the female line. These women are referred to as Dame Firstname Lastname or Dame Firstname (but never Dame Lastname).

Viscounts and Viscountesses

The rank in the peerage below earls and above barons is that of a viscount -- and though it's tempting to pronouce the S, it's actually silent.

A viscount is often be the oldest son of an earl or a marquess, holding his title as a courtesy based on his father's rank. Or he can be the holder of the title in his own right, if it's the most exalted title in the family. A viscount's wife is a viscountess.

His children don't hold titles, other than being formally addressed as The Honorable Firstname Lastname, and the oldest son of a viscount -- unlike the heir of a higher-ranking peer --is treated no differently from his younger brothers.

Today a viscount's daughters are simply called Miss Lastname, regardless of their order of birth. In the more-formal days of the Regency and Victorian eras, the oldest daughter was given a bit more status by being called Miss Lastname, while her younger sisters were known as Miss Firstname Lastname.