You probably know of him as the first Earl of Durham. 'Radical Jack' was the nickname of the very wealthy Durham landowner and Whig politician, John George Lambton (1792-1840), who was created Baron Durham in 1828 and worked on the first (1832) Reform Bill with the Prime Minister (his father-in-law) Earl Grey. He was himself tipped as a future Prime Minister. But the family was consumptive and he resigned from the cabinet in 1834 on grounds of ill health - when he was promoted to Earl.
Did you check the 1901 Census? It's very easy to use and family records cost only 75p. each, which is very reasonable.