Charles Stuart was the eldest son of General Sir Charles Stuart K.C.B., third son of the 3rd Earl of Bute, and Louisa, second daughter and coheir of Lord Vere Bertie, third son of the 1st Duke of Ancaster. He was a diplomat and successively chargé d'affaires at Madrid, Envoy to Portugal, Minister at the Hague, and Ambassador to Paris. In 1812 he was made a Knight Grand Cross of the Order of the Bath, and in 1828 was created Baron Stuart de Rothesay. Afterwards he was Ambassador at St Petersburg. He married, 6 February 1818, Elizabeth Margaret Yorke, third daughter of the 3rd Earl of Hardwicke. They had two daughters, the peerage therefore became extinct at his death. His books were sold at Auction by S. L. Sotheby & J. Wilkinson 31 May 1855. The Royal Library at Windsor has a large number of books that belonged to Lord Stuart de Rothesay and to William Stuart. The latter bought many books at the sale of the former and often added his arms to books that had belonged to him, but were without his arms.