Anne died in 1787, and Robert married again a year later, on 16 January 1788 in London. His second wife was Juliana Barbara Howard (25 June 1769 – 16 April 1833, London), sister of the future Bernard Howard, 12th Duke of Norfolk. Juliana was 19 years old, 27 years younger than Robert, and, indeed, Robert's son had himself married her older sister two years previously. Juliana and Lord Petre had three children:
