My brothers rear axle is bent. I don't have a vice grip so I have nothing to straighten it with. What do I do?
It's unlikely you could straighten it without taking it out of the hub anyway. Once it is out, you can tap it straight with a hammer or anything heavy. However, if it bent once, it will probably bend again unless the first bend was the result of something unusual.
Probably best to get a new axle, preferably a better quality "cromoly" one. Riding with a bent axle may damage the bearings if they didn't already get messed up. But if you have to ride in the short term, at least rotate the axle so the bent ends point down in the frame. That way, his weight will be pushing the bend the other way and will tend to straighten it if he comes down hard on the wheel. Note, don't try to bend it straight by putting a lot of force on the wheel itself. That will definitely mess up the bearings.