In the novel The Sittaford Mystery, Martha Elizabeth Rycroft is the mother of the novelist Martin Dering. According to records at Somerset House uncovered by Inspector Narracott, Martha married William Martin Dering in 1894. Martha Rycroft is also the sister of Mr Rycroft, the resident of Cottage No. 3 in the village of Sittaford. This made Mr Rycroft the uncle of Martin Dering.
As Martin Dering's wife Sylvia is the niece of Captain Trevelyan and stands to inherit a quarter of his estate, this makes Mr Rycroft in Sittaford somewhat connected and an interested party through his nephew Martin and a plausible suspect in the murder of Trevelyan. However this plot element is not developed very far.