@cicerone imposter,
Genetic pools are far more extent then the active visible genes that the parents have...that´s why, they, the kids, some times turn out so different from the moment they were born...of course with environment they change even further.
Although family´s have a preferential "genotype" they probably also have in a smaller amount, (statistics on sperm and eggs variety ) as plane B, some diverse sideline possibility´s...for purposes of adaptation, if conditions change in the future, thus preventing to an extent, extinction... in layman terms "the black sheep" in the family makes proof of this...