The AC codeshare shows C9 rest 0 the LH shows C6 rest zero. The AC flight ex FRA leaves at 10am and is booked out on Sunday. The OS flight ex VIE is also overbooked. Leaves AF and BA which have one or two seats open in their high fare Y booking classes.

Your brother might score an upgrade or be rebooked onto the AF and BA flights, reaching a bit (3-4h) later, so aprox 600€ in vouchers is likely. Tell to dress business casual and volonteer for a rerouting. That should make him suitable for an upgrade.

Here's the official compensation list of LH:

http://konzern.lufthansa.com/en/html...12/214/HOM&s=0