Is genealogy all about genes?

That's not meant to be a trick question, but it is surely a tricky question. And I'm not at all certain that I can indeed reply correctly and intelligently. Both the ancient term "genealogy" (study of generations of ancestors) and the relatively modern biological word "gene" (one of the many molecular elements of an individual's DNA) are inspired by the same root: γενεά ‎(geneá, "generation, descent"). So, the obvious answer to my question is yes: the study of genealogy is surely concerned by some kind of an examination of an individual's DNA. Having made that point, I'm obliged to say that, for the moment, the concrete associations between conventional family-history preoccupations and modern genetic methods are not at all obvious.

It's well known that many everyday family-history enthusiasts are tempted to pay fees to US laboratories specializing in genetic enhancements to everyday genealogy, usually of a complex nature. I made this decision several years ago, without fully understanding the exact advantages that I might (or might not) acquire. I can now say that I derived few avantages of the kind I was expecting, and nothing proves to my mind that the alleged missions of such companies are as sound as they make themselves out to be. On the other hand, an unexpected family-history event enabled me to discover that this kind of enhancement of ordinary family-history research can give rise to a startling result. I'm talking of the extraordinary Courtenay affair concerning the chance discovery of my paternal great-grandfather.

http://skyvington.blogspot.fr/2014/08/chromosomes-reveal-truth.html

On page 48 of The Ancestor's Tale by Richard Dawkins, there's a precise and brilliant explanation of "a telling difference between gene trees and people trees". Here, for example, is a "people tree" of my own childhood family in Australia:

That's me on the middle left, then my brother followed by our three sisters. Now, the questions introduced by Dawkins could be put as follows: In the case of a specific gene that's responsible for such-and-such an aspect of the character of a particular child, did that child inherit that gene from our father or from our mother, and was it the same gene that was inherited (from the same parent) by the other four siblings?

The answers to those two questions astonished me greatly when I first encountered them, and I'm sure that many people might be surprised, for they prove beyond any doubt whatsoever that siblings in a sole "people tree" do not necessarily acquire their specific character traits from the same "gene trees". To put it bluntly, brothers and sisters do not necessarily share identical character traits. Let us imagine, for example, my brother's genes that played a role in making him behave character-wise in a particular fashion. It is perfectly thinkable that none of Don's siblings had inherited comparable genes. Don's gene might have come, for example, from the father of Enid Kathleen Walker, whereas my corresponding version of this gene might have come, say, from the mother of King Mepham Skyvington.

This appears to me as a highly significant and fundamental law of inheritance, which should not be ignored.