Sylvia (Jack's daughter) never married. She raised Henrietta as a single mother, working in advertising (she came up with the slogan “Cheese Please, Louise”). According to Henrietta, her (unnamed) father was in the Guinness Book of Records as 'Britain's Most Married Man': he married seven times but never married her mother, who came between numbers 3 and 4.
(Source: interview by Jeanette Winterson in The Times, 19 June 2003)