What do you mean by "ex"? Ex-spouse? Ex-boyfriend/girlfriend? Spouse you're simply separated from?

If you're divorced, look at your divorce judgment.

If you're on the loan and your ex- isn't paying, it's harming your credit. If your ex- defaults and they foreclose, that goes on your credit and they can come after you for the deficiency.

Talk to your lawyer, and be a bit more earnest.