James Boswell's uncle John was a member of a sect known as the Glasites.
Willem Bentinck van Rhoon
Willem Bentinck van RhoonBorn 1704
Son of Hans Willem Bentinck, 1st Earl of Portland. Created Count by Emperor Karl IV in 1732. Married (1733) to Countess Charlotte Sophie von Aldenburg. They divorced in 1740. Father of Christian F. A. van Bentinck.
Note 1: I am a bit unsure if this is in fact the Comte de Rhoon referred to by Boswell. Willem Bentinck was Heer van Zorgvliet, while his son, Count Anthony Bentinck (1734-1768) was Heer van Rhoon at the time of his death in 1768. Add to this, that Anthony married in 1760 Maria Catharina van Tuyll van Serooskerken, a daughter of Baroness Ursulina van Reede, the aunt of Arend van Reede, who accompanied Boswell to visit the Comte de Rhoon. Anthony's brother Johan Albrecht Bentinck coincidentally had married another daughter,Reiniera van Tuyll van Serooskerken, of Ursulina van Reede in 1763. It does seem, however, that Boswell consistenly referred to Willem Bentinck as Count Rhoon, and to his son as Count Bentinck.