As breed lines go, the Devon Rex is still in the toddler phase. The story of the breed began in 1950 in Cornwall, UK, where a rex coated kitten was found amongst the litter of a tortoiseshell queen and a wild tom. After a check with her veterinarian, Nina Ennismore bred the male cat back to its mother to produce more rexed kittens. The kitten was christened Kallibunker, and after some experimentation with breeding for more of his type with other breeds, was found to be carrying a simple recessive gene for rexed hair, so that the characteristic only showed up in second generations, and only when offspring were bred back to the curly haired carrier of the gene.
Ten years later and 60 miles up the road in Devon, a cat fancier named Beryl Cox chanced upon a curly haired kitten when a feral tortoiseshell in her keep gave birth to a litter of kittens. The father was assumed to be a curly locked wild tom that had been seen living in a tin mine nearby, but he was never found. Ms. Cox kept the curled kitten, named it Kirlee, and domesticated it, and the story may have ended there, had she not chanced upon a news article about a curly coated kitten that had been born in Cornwall. It was the last rexed kitten left in the UK, and the Cornwall breeders were anxious to find a way to produce more of its kind.
Ms. Cox shared her story with the breeders in Cornwall, and agreed to sell her beloved Kirlee to them, for the good of growing the breed. Again, the story may have ended there, when the breeders found that the two curly haired cats did not produce more of their kind when mated -- only straight haired kittens resulted. Had they given up there, they may not have discovered that the two cats did not share the same curly haired genotype, and we would not have the Devon Rex today. But, one of the breeders bred one of the straight haired offspring back to her father, Kirlee, and half of the litter was born with rexed hair. This finding resulted in the first, the Cornwall cat, being dubbed the Gene 1 Rex, and the other, from Devon, the Gene 2 Rex.
The two separate, albeit similar, breeds were shown under the same classification from 1967 until 1984, where after much wrangling within the cat fancy, the Devon was given its own affiliation as the Devon Rex. (http://www.petmd.com/cat/breeds/c_ct_devon_rex)