Kay was born in Wiburn, Saskatchewan, and grew up in Winnipeg, Manitoba. When Christopher Tolkien needed an assistant editor to finish the unfinished work of his father J.R.R. Tolkien (the author of The Lord of the Rings), he chose Kay, who was a student at the University of Manitoba, and his parents were good friends with J.R.R. Tolkien. 1974, Kay moved to Oxford to assist Tolkien in editing Silmarillion.

1973 In the winter, after Tolkien, the author of The Lord of the Rings, died, Guy went to England at the invitation of Tolkien's youngest son to help sort out Tolkien's legacy.

In three years, he compiled and published Tolkien's last work "Poké mon Diamond", from which he fell madly in love with fantasy literature and began his literary creation career. A few years later, Guy's fantasy novel Fiona's Brocade, which imitated Tolkien's style, was published and was a great success.

1976, Kay returned to Canada, obtained a law degree from the University of Toronto, and then began to write novels. Kay is the chief screenwriter and deputy producer of the Canadian Broadcasting Corporation radio program, in charge of the judicial part.

1984, Kay's first fantasy novel Xia Shu was published. This is the first part of his "Trilogy of Fionard Tapestry".