The twins, Janet and Anne Grahame-Johnstone, were born in 1928 to successful British portraitist and costume designer Doris Zinkeisen and her husband, Captain Edward Grahame Johnstone. They attended the Heathfield School in Ascot, Berkshire during World War II where their artistic talent was nurtured. Later, they attended Saint Martin's School of Art in London, where they studied period clothing styles before moving to Suffolk in 1966. The twins never married and would both live with their mother until their deaths.

Janet died in 1979 due to smoke inhalation following a fire in the kitchen, leaving Anne on her own for the first time in her life. Their brother, Murray, described them as one and a half of each other, rather than two people. Suddenly Anne was solely responsible for their entire business enterprise and managed to honour all their outstanding commissions. She had to master the techniques for drawing and painting animals, particularly horses, which had been the specialty of her sister. Eventually she became so good at it that she was elected a Member of the Society of Equestrian Artists in 1998. Anne died of liver cancer in Badingham, Suffolk on 25 May 1998.