Robert King, the presumed sitter, was the eldest son of Sir Henry King, 3rd Bt., and his wife Isabella, sister of 1st Viscount Powerscourt. Robert was baptised on 18 February 1724. He was elevated to the Peerage and Ireland on 13 June 1748 as Baron Kinsborough. He died unmarried on 22 May 1755, and the baronetcy devolved upon his brother Edward.