Buying bank note or short sale

[Brandi Lynne Corley]

My husband is a successor in interest on a bank note that his deceased mother had.  My mother in law purchased a home for her youngest son and hid wife at the time.  My ex- sister in law signed the mortgage and is on the deed as a joint tenant with right of survivorship but she is not on the bank note.  My mother in law made all the payments on the house,  but instead of her two sons getting the house,  my ex sister in law did, along with much much more- all done underhandedly! The is $70,000 still owed on the house. My ex sister i in law has it up for sale for $260,000. Now it is 2 months behind in payments since she has been forced to take them over because we will not make the payments for her to receive all the profit.  The bank is contacting us repeatedly. Can my husband buy the bank note from the bank?  Is there a better course of action here? Please help focus us in the direction! Thank you!