Mild to moderate hiatal hernias are a normal aberration in older patients, and there hasn't been a proven connection with reflux. (I don't have an exact number, but I would say up to 2.5 to 3cm.) Once they progress beyond this size, they can become problematic.
Because the hiatus in the diaphragm gets looser as we get older, sliding hernias are a result. Most of the time, the esophagus stays in place, but under certain conditions can slip above the diaphragm. If the GI is inexperienced, or not trained to expect this result, he can overfill the stomach with gas during an EGD which will force the fundus to balloon and push beyond the hiatus. This is true in my case. In the past I was measured with a 2.5cm. hiatal hernia, then on a later EGD, none was located.
A few weeks ago, PPI-LESS posted a link to a YouTube video of a doctor performing a Nissen. During the procedure, the doctor commented on the three most common indications for a failed Nissen, which I would assume would also be true for a failed hiatal hernia correction. The first he called the "Aunt Bea" body type, or a woman with a stocky build and large abdomen. The second was weight-lifters, and the third was those who had been in car accidents.
GIs aren't usually concerned with a hiatal hernia if it is within the range that I described, and there are no other indications. As far as a genetic connection goes, that sounds logical. I'm sure OSHA would be interested in you having to lift 75 pounds on the job...