Kathleen Clarice Louise Cornwell was born on 11 March 1872 in Melbourne, Australia. She was the daughter of Jemima Ridpath and George Cornwell, married in 1850. Her father was a railway guard who became a successful gold prospector in Australia, operating several mines, her eldest daughter, Alice Cornwell (1952), did a great deal to assist him, and the family became spectacularly rich by the 1890s, and they returned to England, where Alice Cornwell (Stennard Robinson) bought the Sunday Times newspaper.

On 19 February 1890, at 17, Kathleen Clarice became the second wife of Herman Klein (1856-1934), an English musical author, teacher and critic, who was 16 years older than her. He had a daughter Sibyl Klein, from a previous marriage, and they had two sons: Adrian Bernard Klein (1892-1969) and Daryl Klein (1894) and a daughter Denise Naomi Klein (1897-1985). During her marriage with Klein, Kathleen Clarice began an affair with a young man, Herbert Arthur Berkeley Dealtry (1878), who was a Worcestershire Regiment officer. When Herman Klein became aware of it he filed a petition for divorce, which was granted in December 1901. After the divorce Kathleen Clarice married with Dealtry in 1902. The marriage was going through financial difficulties and Dealtry had to declare bankruptcy in 1905, and they left for America with her daughter, Denise Naomi. Some years later, Kathleen Clarice returned to London, and in 1918, she married for a third time with Sydney H. Groom.

Kathleen Clarise, who wrote several short stories in Magazines and novels under diferent pseudonyms (playing with her diferents names and surnames), started a saga of popular writers. Her eldest son Adrian Bernard Klein, changed her name to Adrian Cornwell-Clyne, and became an artist, who wrote books on photography and cinematography, and her daughter Denise Naomi Klein also followed in her footsteps and became the popular romance writer Denise Robins, who was the first president of the Romantic Novelists' Association (1960-1966). Her granddaughter Patricia Robins (aka Claire Lorrimer), who is Denise Robin's daughter, is also a popular romance writer.

Kathleen Clarise pased away in the Brighton/Hove area in 1954, aged 82.