The different dreams could mean different things for each of you. The gun can be a phallic symbol. In your case the fact that you dreamt of a car could be that someone is trying to overpower you psychologically or sexually and that you are feeling that you have no control of the situation.
The fact that the car is red could be a symbol of passion or anger. The gun can also be a symbol of control or power and you and your friends maybe feeling powerless in your personal lives.
Try to think what it could be referring to in your lives and think what you can do to get control of the situation. The fact that your brother dreamt of a hotdog, which is clearly another
phallic image, could also be sexually related. Make sure there isn't anyone you know who has some control in your life and who is trying to take sexual advantage of you or your friends.