It's a tough call. My first reaction was to tell you, as one person already did, was to go to the police and file a report. However and unfortunately, with this amount of time passed, it could be a he said, she said kind of outcome and you have to consider the reaction of your family and if they are worth keeping around.
If you feel no one believes you, and the cousins would just deny it anyway, are they really worth having around?
Even then, do you want the hassles of rehashing this over again in a court system that may or may not be in your favor and everything you have done of questionable character in the past will be brought up to discredit you.
Your best bet is to follow some of the others advice and seek counseling without any further delay. You will feel better and you will have an impartial person who can guide you in the right direction. But in the end, it has to be what you and only you want.
Take care. I am not a victim, but I have a young daughter and a young son and if this happened to them, I'm afraid I would be in jail for reacting first and asking questions later.