 Middleton outlived his eldest son Gilbert (b.1873) and was succeeded by his son Sir Charles Middleton, 8th Baronet (1874–1942).He was the author of "An Account of Belsay Castle in the County of Northumberland", published in 1910, and of "Sir Gilbert de Middleton and the Part he took in the Rebellion of the North in 1317", published in 1918.