Auto Insurance Claims: Release of accident claims, subrogate, other vehicles

Question
My boyfriend was recently involved in a multi-car accident.  It was raining that day so the roads where somewhat slippery.  The car in front of him stopped so he braked and barely touched the other car's rear bumper.  However the car behind him was unable to stop in time and hit my boyfriend's car which in turn hit the first vehicle with more impact.  There are two other vehicles involved (5 total).  The first car and my boyfriend's did not have much damage but the last three cars did, probably due to tailgating and not having enough space to stop.

The first vehicle is demanding my boyfriend to pay-up.  He's not asking much, but I was wondering if he's in a position to make such demands.  His vehicle was barely damaged.  Should my boyfriend pay and get an accident release signed?  Is he now supposed to turn around and make the same demand from the vehicle that hit him?  The third vehicle owner is refusing to make any payment or offer any settlement so I'm wondering what his next course of action should be.  What options does he have?

Who should be responsible for the whole accident anyway?  My boyfriend barely touched the first car, but because of the chain reaction behind him, he ended up looking responsible for whatever damage the first car sustained.

I hope my story makes sense.  Whatever opinion you may have on this matter will be greatly appreciated.

Answer
Have your boyfriend submit the claim to his insurance company with the details of the accident. Be sure to name the driver of car #3 and mention that his impact drove your boyfriend into car #1. His company will pay the damage repair to car #1 and subrogate the claim with the insurer or the driver of car #3.