Harold Frederick Shipman (14 January 1946 - 13 January 2004) was a British general practitioner and one of the most prolific serial killers in recorded history. On 31 January 2000, a jury found Shipman guilty of fifteen murders for killing patients under his care. He was sentenced to life imprisonment with the recommendation that he never be released. The Shipman Inquiry, a two-year-long investigation of all deaths certified by Shipman, which was chaired by Dame Janet Smith, examined Shipman's crimes.

Harold Frederick Shipman was born on the Bestwood council estate in Nottingham, England, the second of the four children of Harold Frederick Shipman (12 May 1914 - 5 January 1985), a lorry driver, and Vera Brittan (23 December 1919 - 21 June 1963). His working-class parents were devout Methodists. Growing up, Shipman proved himself an accomplished rugby player in youth leagues.  In 1957 he passed his eleven-plus moving to High Pavement Grammar School, Nottingham where he left in 1964. He excelled as a distance runner and in his final year at school, served as vice-captain of the athletics team. Shipman was particularly close to his mother, who died of lung cancer when he was seventeen. Her death came in a manner similar to what later became Shipman's own modus operandi: in the later stages of her disease, she had morphine administered at home by a doctor. Shipman witnessed his mother's pain subside despite her terminal condition, up until her death on 21 June 1963.  On 5 November 1966, Shipman married Primrose May Oxtoby. They had four children.  Shipman studied medicine at Leeds School of Medicine and graduated in 1970. He started working at Pontefract General Infirmary in Pontefract, West Riding of Yorkshire, and in 1974 took his first position as a general practitioner (GP) at the Abraham Ormerod Medical Centre in Todmorden, West Yorkshire. In 1975, he was caught forging prescriptions of pethidine (Demerol) for his own use. He was fined PS600 and briefly attended a drug rehabilitation clinic in York. He became a GP at the Donneybrook Medical Centre in Hyde near Manchester, in 1977.  Shipman continued working as a GP in Hyde throughout the 1980s and began his own surgery at 21 Market Street in 1993, becoming a respected member of the community. In 1983, he was interviewed on the Granada Television documentary World in Action on how the mentally ill should be treated in the community. A year after his conviction, the interview was re-broadcast on Tonight with Trevor McDonald.

Using a quote from the above article, answer the following question: Did they have children?
They had four children.