Ken Wainwright's father, Job Henry Wainwright (aka Harry), was born in 1882 in Dudley, Stafffordshire, England, several miles west of Birmingham. He worked as a grocer's assistant and came to Canada in 1906. His older brother Frederick and his wife arrived in Toronto in 1908 and the Wainwright brothers set up a grocery and butcher shop on Davenport Road near Old Weston Road in the village of Carlton.

On June 22, 1914, Harry married May Beatrice O'Connor, a widow two years his senior. May was born in London, Ontario, the daughter of Dr. William O'Connor, a medical doctor and MA, who taught at Trinity College in Toronto in the 1890s. She had been married in 1906 to widower Samuel E. Jewitt, the principal of Carlton Public School (today's Carleton Village Public School), which in 1907 was located a block west of the current school, on the parking lot of today's 11 Division police department. Jewitt suffered poor health for the last year of his life. When he died in 1908, he had been the school's principal for about 20 years and he owned fifteen houses and empty lots mostly in the Carlton neighbourhood, leaving an estate of $17,279 which was split evenly between his two daughters from his first marriage and May. One of the properties which Jewitt owned was a parcel of land on today's Prince Edward Drive worth $3000. May was also bequeathed their house at 60 Kingsley Avenue and continued to look after her stepdaughters who were in their teens when their father died. She probably met Harry when shopping at the Wainwrights' store in her neighbourhood.

Harry opened a grocer's next to his brother's butcher shop in 1916 and by the time Ken was born on August 5, 1919, he and May had a grocer's at 2565 Dundas Street West, south of Annette Street and they lived above the store. In the fall of 1923, they moved to 464 Prince Edward Drive, which may have been part of Samuel Jewitt's estate and Harry continued to run his grocery store on Dundas Street.

Ken started school at Lambton Mills in September 1924. By 1927 the family was back living above the store and Ken transferred to Keele Street Public School. Harry ran the store until 1932 when he retired. It is unclear where the family was living until 1938, but Ken remained a pupil at Keele Street until June 1932. The Wainwrights may have moved back to Etobicoke for a year as Ken attended Etobicoke High School in the 1932/33 year. He spent a year at Humberside Collegiate from 1933 to 1934 and attended Western Tech from 1934 to 1939, graduating with his senior matriculation. By 1938 the Wainwrights had settled at 25 Indian Road Crescent, but they presumably had lived in that neighbourhood since 1933.

Ken occasionally played baseball, rugby, golf and badminton. He enjoyed Chemistry at school along with Drafting and he had the sort of mind that liked to tinker with mechanical and electrical apparatuses. From November 1933 to October 1935 he was a Signalman, mainly a stretcher bearer, in the 2nd Division of the Canadian Corps of Signals but left because it was interfering with his school work. A few days before he started a Christmas job at Eaton's department store on December 1, 1938, his name was in the papers listed as one of the four hundred guests at the Western Tech-Commerce graduates' Christmas Dance at the Boulevard Club on November 29. After graduating in June 1939, he had a job at the Exhibition in August working for Silverwood's Dairies.

That November, he found a permanent job as a junior bank clerk at the Lawrence Park branch of the Dominion Bank, which he left to join the RCAF on July 1, 1940. He undertook his basic training at the Exhibition grounds in Toronto and on July 22, he began his Initial Training at the school on the old Toronto Hunt Club grounds near Avenue Road and Eglinton Avenue. The summer of 1940 was early in the Commonwealth Air Training Plan and later procedures were not yet in place. The speed of the training was about 25 percent faster than it would be a year later.

By mid-September Ken was chosen to be a pilot and he began his elementary pilot's training at Malton (today's Pearson airport), flying Tiger Moth bi-planes. Ken was an anomaly as the RCAF was only taking licenced pilots and university graduates for its pilot program at the time. How he was able to be considered is unknown. On November 16, Ken had graduated to the Service Flying Training School at Uplands airport, near Ottawa. On January 28, 1941 he was promoted to Pilot Special Grade and probably was given a two week embarkation leave before reporting back to Ottawa.

Unlike most RCAF personnel, who shipped out of Halifax, Ken flew from Ottawa to Britain on March 6. As it was early days in the arrival of Commonwealth air personnel in the United Kingdom, and the RCAF Personnel Reception Centre in Bournemouth wasn't yet established, Ken was sent almost directly to No. 19 Operational Training Unit (OTU) at RAF Kinloss and Forres in northeast Scotland. The unit trained night bomber crews on the Armstrong Whitworth Whitley medium bomber. It carried a crew of five: a pilot, a co-pilot/navigator, a bomb aimer, a wireless operator and a rear gunner.