There's an excellent biog of Sandy (if you can get ahold of it: it seems to be out of print) which mentions David, and chronicles her life pretty thoroughly. Well worth buying anyway, though it's mostly about her. But it does give some family background, and does mention his sad death. I also think there's at least one photo of the two of them as children, maybe more. David seems to have always been a true friend and support to Sandy. How terrible that both their lives were so brutally cut short. You can see more at

Amazon.co.uk (the British outlet)

Please let us know what you manage to come up with and keep us up to speed - it's a very interesting topic. Best of luck in your findings!