 According to Serres, Wilmot had secretly married Princess Poniatowski, sister of King Stanislaus I of Poland, and thus Wilmot was actually her grandfather rather than her uncle.Wilmot had fathered a daughter, Olive, and had officiated at her secret marriage to Prince Henry, the Duke of Cumberland in 1767 at the London house of a nobleman.Serres produced a document signed "James Wilmot" asserting that he had conducted this marriage.