...If I had not been wearing a bike helmet last Saturday, it's entirely possible that I would not be here to talk to you (or host this site anymore) today.
I was on a training ride for the American Diabetes Association Tour de Cure (for which I am the Vice Chairman this year), and my rear tire slipped out from under me on a wet wooden bridge while I was going along at about 17 mph. I landed on my shoulder, my hip, and my head, in that order. My head slammed the ground pretty damn hard, and I would have AT LEAST ended up with a fractured skull, if not worse.
As it is, I have a broken left thumb and a sprained right shoulder.
I've been riding pretty hard for 12 years and over 6000 miles. This is the first major accident I've had. While I've never before had a personal story to tell about wearing bike helmets, I have always done so. Now I do, and I will (of course) continue wearing the new one I'll purchase once the thumb/shoulder heal.
Sorry about your brother. Seems pretty senseless to not wear a helmet. :(