A.N. Devers debunks the myth:
The story goes like this: the scores of cats that have lived over the decades on the property in Key West are direct descendants of Hemingway’s original cats, including Snowball, a six-toed cat who was given to Hemingway as a gift from a sea captain. When I visited in 2008, the Key West guide showed off a picture of Hemingway’s young son Patrick, holding a snow-white kitten in the yard. But in a 1972 Los Angeles Times article by Charles Hillinger, Ernest Hemingway’s last wife and widow, Mary Hemingway, states, “Ernest…never kept animals at the Key West house during the last twenty years of his life. He never stayed at Key West long enough to bother with animals after his divorce from Pauline.”
In a 1994 interview with the Miami Herald, Patrick Hemingway stated the cats in the picture were his neighbors’ who wrote in to the paper to confirm. The cat myth began with Bernice Dickson, who bought the Hemingway house in 1964 and opened the estate as a tourist attraction. At some point she started breeding and selling six-toed cats, even sending them through the mail, and claming, “they are a special Asiatic breed that Mr. Hemingway had when he was here.”
The Dish 