 He was the eldest of the three sons of the 2nd Duke of Cambridge and Louisa Fairbrother (the other sons were Admiral Sir Adolphus FitzGeorge and Colonel Sir Augustus FitzGeorge).As his parents were married in contravention of the Royal Marriages Act 1772, he was ineligible to succeed his father as Duke of Cambridge and along with his siblings did not hold royal titles.Through his father, he was a great-grandson of King George III of the United Kingdom and first cousin to Queen Mary.