Not that anyone asked but . . .
Duke
Wife : Duchess
Style : His Grace the Duke of ______
Addressed : My Lord Duke or Your Grace
Eldest son : Takes on a secondary title of the duke (if there is one, always is one in Britain) as a curtesty title.
Younger sons and daughters : Lord or Lady (christian name)
Marquess
Wife : Marchioness
Style : The Most Hon. (Honorable) the Marquess of ______
Addressed : My Lord Marquess
Children : Same as Duke above.
Earl
Wife : Countess
Style : The Right Hon. the Earl of ________
Addressed : My Lord
Eldest son : As Duke above.
Younger sons : the Hon. (christian name)
Daughters : Lady (christian name)
Viscount
Wife : Viscountess
Style : The Right Hon. the Viscount of _________
Addressed : My Lord
Children : the Hon. (christian name)
Barons
Wife : Baroness
Style : The Right Hon. the Baron of ________
Addressed : My Lord
Children : no honorific
Baronet
Wife addressed as : Your Ladyship or Lady (surname)
Style : Sir (name), Bt. such as Sir George Windsor, Bt.
Addressed : Sir (christian name)