If you were solely the authorized user of your "ex" and nothing more, then you would not be responsible to pay the credit card bills directly to the credit card company assuming the credit card that you are writing about was not in your name for billing and obligation purposes.However, there may be some agreement between you and your "ex" that even though he or she was primarily responsible for paying the credit card debt on a credit card that you were authorized to use, you may be obligated to him or her for reimbursement of any monies paid for your use of the credit card. From what you have written, I do not know what agreement you may have had with your "ex" concerning the ultimate repayment for the credit card's use.Good question.