Lawson's mother died of liver cancer in Westminster, London at the age of 48. Lawson's full-blood siblings are her brother, Dominic, former editor of "The Sunday Telegraph", sister Horatia, and sister Thomasina, who died of breast cancer, in her early thirties, in 1993; She has a half-brother, Tom, who is currently headmaster at Eastbourne College, and a half-sister, Emily; Tom and Emily are her father's children by his second wife. Lawson is a cousin to both George Monbiot and Fiona Shackleton through the Salmon family.