It's not just genetic dependent. If a female produces pollen to self-pollinate, then the seeds of that plant, will be 50/50 in most cases as to whether they grow properly, or turn hermied. You can have a 'strong' family genetic..everyone lives to be a hundred, but if suddenly 2 siblings or cousins in that family reproduce with each other..suddenly you have a possible genetic mutation, and the offspring will not be in the same kind of health as the rest of the 'properly' produced members of that family. Yes, some our great strains were produced by hermies, but not in one instance..it took years of breeding and cross-breeding back and forth to make said seed, stable.