Sorry to hear about this but to be honest I'd have expected it. There will always be a faster, cleaner, more conscious worker. It only works when they are actually labourers because you brush off their **** with them being labourers and put it down to practise and give them guidance etc etc to try and make them better.
When it's your brother who should know a lot better - you're just at a lost cause there's nothing he'll learn from you if he hasn't already in 12 months.
If you're after an easy way out perhaps give him the smallest contract, you keep the rest, and tell him if you get good feedback you'll pass him another WHEN YOU CAN (don't promise anything or give names or dates etc - he wont get good feedback I wouldn't have thought).
I respect you for trying to help. But you can't help them all mate.
You're prolonging the inevitable if you keep working as you are as you will pop again when it bottles up again.