See, this is why I make a regular point of sharpening the machete in front of my family.
Anyway, you might want a more professional piece of file recovery software. They're around $200, but make your brother pay for it- seriously. Exaggerate the importance of the stuff on there whenever possible, ***** endlessly to your parents, and don't let him over again for at least a year- he'll get the message and never touch your machine again. Trust me on this. It might make you unpopular among your siblings, but being a horrible asshole when it comes to computers keeps your files intact- I haven't been virused once since I took to forcing mine off regularly on slight pretexts and deleting their MP3s when they land in my folders.