Saotome Genma was a migrant worker on a Midwestern farm in the days before the Great Depression. He and his wife, Nodoka, had left Japan many years before after a dispute with his family over the inheritance of their traditional dojo, and they were fortunate to get in before the United States Congress tightened immigration laws to specifically exclude Asians, and since most other lines of work were forbidden to Chinese and Japanese citizens, being a farm laborer for the Kents was a matter of happy serendipity. For all that they were content to live as foreigners in "The Land of the Free," they were dirt poor and barely struggling to make an existence together. Unfortunately their marriage was (as yet) largely childless, and that weighed heavily on Genma's consciousness whenever he saw her looking at some other happy family playing with their children.
But one day, while delivering supplies from the local town of Smallville, a chance came to change all that when he and his wife saw a meteorite come crashing down very close to the Kent's truck that they were driving. Against the sage council of Genma, who wanted nothing to do with any crashing foreign objects from another planet, Nodoka had been drawn to the sound of a baby's crying, and---sure enough---they discovered an infant in the cornfields next to the damaged space rocket. A brief debate broke out over what to do over the matter, but as Genma could never truly bring himself to say no to Nodoka (especially since she still kept their family sword upon the mantle) he eventually caved in and acceded to her wishes.
Having to explain to the Kents how they had suddenly acquired a two-year-old son from seeming no where took a bit of ingenuity on his part, but Genma was nothing if not creative in the art of telling tall ones.
Of course the discovery that their newly acquired child was something more than just another potential farm hand came rather suddenly one day when Genma was working on a tractor, and little baby Ranma chose to play with his daddy's new tool by picking it up off its rack and holding it up for easier access that did not involve using a jack or some other mechanical contrivance.
After a bit of panicked realization of what this would mean if someone were to ask why their six-year-old boy was so amazingly strong, Genma confided in Nodoka that the real reason for their leaving Japan had to do with his desire to escape from the clutches of his perverted old master, and if word of the boy's unusual talent were ever to make it back to the Home Islands...well...it wasn't just the United States government that might have something to say about the matter.
Of course this brought home the other realization which Genma had "conveniently" failed to tell Nodoka...about a certain agreement that he had made with a neighboring family concerning their son and three beautiful daughters, Lorelei, Lana and Lois, which was another reason for Genma and Ranma to keep busy on their periodic training missions which took them all over the world and even to the very depths of China...