[Citation required] for almost every sentence in your post - most importantly "it is the backbone driving the most valuable members of our society". What a ridiculous assertion.
It's easily verified by data you can find in many studies, and presumably the census itself. Of course it doesn't technically prove causality - it could be that the type of people who are successful just happen to be the same type of people who get married. Or maybe they get married precisely because they are successful - or unsuccessful people have a harder time finding spouses.
But that's totally orthogonal to the statistic under discussion about people living near their blood-relations. You can move across the world and still get married, or live nearby and never.