If my divorce decree says that my Ex is responsible for the debt of the second mortgage, can the credit union sue me for half?

Assuming that the credit union you refer to is the holder of the second mortgage, they can take whatever actions they are allowed under your state's laws to take their collateral assuming payments are not made to them.  Usually this is foreclosure.  If there is a deficiency amount owed after the foreclosure (or other) sale, they can sue you for that amount.  Your divorce decree does not affect your creditors at all.  It is a decree between you and your ex and only affects what you owe each other.   It does not, and cannot, affect contractual relationships with third parties.   Mark J. Markus, Attorney at Law Handling exclusively bankruptcy law cases in California since 1991. http://www.bklaw.com/ bankruptcy blog: http://bklaw.com/bankruptcy-blog/ Follow Me on Twitter:  @bklawr