Since all three of you did not go in and do a joint claim so the winnings could be split three ways along with the withholding.... Then here is my suggestion.
The person who handed in the ticket and who social security number the winnings were reported in will file a return with all the winnings and all the withholding.
First that person completes his return without the winnings and notes the bottom line. Then that person adds the winnings and the withholdings and again notes the bottom line. Then the difference in the bottom line is what is a tributed to the gambling winnings. Divide that by three and have the other two pay their share to the person who's reporting the gambling winnings. This is the simplest way to fix this situation and keep the IRS from sending anybody stupid letters in the future.
