[1] His only sibling was Francis Trajan Sacheverell Sitwell, member of the Council of the London Philharmonic Orchestra who lived at Weston Hall, Northamptonshire.
[2] His paternal grandparents were Sir George Sitwell, 4th Baronet, of Renishaw Hall, and the former Lady Ida Emily Augusta Denison (a daughter of the 1st Earl of Londesborough and a granddaughter of the 7th Duke of Beaufort).
His maternal aunt was Frances Doble, an actress who had a short career on the West End stage in the 1920s and 1930s before her marriage to Sir Anthony Lindsay-Hogg, 2nd Baronet.
He was succeeded in the baronetcy by his nephew, George Sitwell, the son of his brother Francis, who died in 2004, and his sister-in-law Susanna Cross.
[8][2] Due to Sir Reresby and his brother being "never in harmony",[9] he bequeathed Renishaw Hall to his daughter, and only child, Alexandra.