Where are you based and what kind of hardtail is your brother looking for?
I've been looking for a road bike for a while and I have a GT Avalanche 1.0 2008 (Large 20"). It's had it's wheels and brakes upgraded but is setup as a single speed at the moment so it's doesn't have gears like you'd expect.
I may be interested in a swap, if he's interested let me know and we can discuss it more.