Your brother is quite correct. In fact, that wiki article seems to do quite a good job of explaining it correctly - it's clearly been written by a physicist!
We did have a long discussion on this topic in the Aircraft Customisation forum a few months ago - and we also eventually arrived at the conclusion that Bernelli was not a good way of explaining it.
I fly through the valley of death, but I fear no evil,for I am at 80,000 feet and climbing. Let's powerdive and scare that poor soul in that Ultralight there.