Regarding the brother, if you have access to him while he's sleeping, smash (and break) his right shin with a cricket bat or metal pole while he's asleep. When he awakes screaming insist it was a delayed injury from the accident, and you were just playing cricket/metal-pole-swinging.
Otherwise, if you are worried about him dying when he does get a car, just keep sabotaging it, removing plugs/cables etc. OR fill a cylinder or two with water to keep the power down!
In all seriousnessnessness though, it's a bit awful for you, as even though he's a loser, I assume you don't want him dead. (If you do, call 0181 811 81 81). Send him on a driving course perhaps? Though he might just dismiss it all.
I don't know, plant drugs in his car, feed him alcohol and when he gets in the car call the po-po. You only have to keep thinking of things till he's about 75.