On 26 September 1839, while still an Oxford undergraduate, Bentinck married his first wife, Sinetta Lambourne, daughter of James Lambourne, a horse dealer with some claim to be the founder of Summertown, Oxford, where he lived with his wife Sinetta Smith, a gypsy.
On 26 September 1839, while still an Oxford student, Bentinck wedded his first wife, Sinetta Lambourne, daughter of James Lambourne, a horse trader with some claim to be the originator of Summertown, Oxford, where he resided with his wife Sinetta Smith, a gypsy.