HELP ME! what do I do? Do I pay for it? Split it? or nothing?

So the other day was snowing really bad. My Brother's car was parked on the road and the plows were getting ready to come out. My husband offered to move his car out of the road because he was going outside. He coudlnt back the car up, or pull in the neighbors driveway (they are jerks) so he drove to go around the block and come in the driveway from the opposite direction. The first turn the breaks locked and he went in the ditch. He was driving under the speed limit (25) but lost control when the breaks locked. It wasnt that bad because it kinda just slid in slowly but the large amount of snow that we had caused the bumper bracket things to break. So they need a whole new bumper . They want us to pay for it. I dont think its fare for them to have to but at the same time I dont think its fare that we should shell out the $900 it was an accident.. They refuse to turn it in to insurance and I dont want to caus problems but I dont know what to do. HELP do I pay for it?