Mary, married firstly Lieutenant Colonel John Chichester, son of Edward Chichester, 1st Viscount Chichester. Their son Arthur Chichester, 2nd Earl of Donegall,  inherited the earldom from his uncle.
Lady Mary's first marriage was to Lieutenant Colonel John Chichester, the son of Edward Chichester, who became the 1st Viscount Chichester. Their child, Arthur Chichester, later inherited the title of Earl of Donegall from his uncle.