Personal data
William Petty
Born May 2, 1737  
in Dublin
Died May 7, 1805  
at Berkeley Square, London
1st Marquess of Lansdowne
The Earl of Shelburne

Son of John Fitzmaurice (1706-1761), 1st Earl of Shelburne. Married (ca. 1764) to Sophia Carteret (1745-1771), daughter of the 1st Earl Granville, with whom he had at least one child.1 Married (ca. 1779) to Louisa FitzPatrick (1755-1789), with whom he had at least two children.2

Boswell met Petty, Lord Shelburne, when he called on William Pitt on February 23, 1766, in London. Pitt was an ordinary MP at the time but he was appointed Prime Minister later that year and included Shelburne in his government as Southern Secretary.

    William Petty, 2nd Earl of Shelburne (Wikipedia)

    Unless otherwise noted, the source for a dated quotation of Boswell's is generally the corresponding volume of the Yale Trade Editions of Boswell's journals.