Wesley was born at the family estate of Dangan Castle, near Summerhill, a village near Trim in County Meath, Ireland.

[5] Like his father, and his mother-in-law Lady Dungannon, he was careless with money, and his early death left the family exposed to financial embarrassment, leading ultimately to the decision in the nineteenth century to sell all their Irish estates.

[6] As a composer, Lord Mornington is remembered chiefly for glees such as Here in cool grot (lyrics by William Shenstone) and some Anglican chant.

[7] But he also composed some large-scale music such as the five-act opera Caractacus (libretto by William Mason), first performed at the Theatre Royal, Smock Alley, Dublin on 26 March 1764, and the Ode for the Installation of the Duke of Bedford at Trinity College Dublin, 9 September 1768, for choir and orchestra, of which only an orchestral march survives.

[10] They had nine children, most of whom were historically significant, including:[11] Four of Lord Mornington's five sons were created peers in the peerages of Great Britain and the United Kingdom.