Answer
In 1839, Henry Temple, 3rd Viscount Palmerston and Emily Lamb, Lady Cowper were married.
Emily Temple, Viscountess Palmerston, styled The Honourable Emily Lamb from 1787 to 1805 and Countess Cowper from 1805 to 1839, was a leading figure of the Almack's social set, sister of Prime Minister Lord Melbourne, wife of the 5th Earl Cowper, and subsequently wife of another Prime Minister Lord Palmerston.