Bentinck was born in The Hague, Dutch Republic on 20 August 1764. He was a grandson of Willem Bentinck van Rhoon, and a relative of William Cavendish-Bentinck, 3rd Duke of Portland. In 1795, after the Batavian Revolution, he moved to Great-Britain where his grandfather lived. In 1804, he was a Major in the 2nd Yorkshire Regiment. The colony of Surinam had been taken by Britain, and it was decided to appoint a former Dutch citizen as the new governor.
