Will Sallie Mae negotiate past due $ for this?

My husband has a loan through Sallie Mae that his parents were paying for and he never had to look at a single bill with them. His parents ped away 2 years ago and he didn't know that there was still money due on those loans and now it is in collection. Will they negotiate anything or is there anything I can do so they don't try to garnish anything and so we can get his credit fixed?