Default loan and unable to pay. PLEASE HELP

Hi. I am currently a senior college student and I made a horrible mistake during my senior year in high school to go to an expensive out of state school. My dad signed for a parent plus loan which I didnt think we would have to repay until graduation. We borrowed a total of 30k from sallie Mae ( and has now been bought by Pionner Recovery) and our loan have recently went into default because my dad had became unemployed for the past year and my family is currently living on food stamps. Since my dad has no income and has been living on food stamp for the past years, we are not sure what to do. there is no possible way for us to pay anything. Can anyone please give me some good advice on suggestion on what we should do.

Pioneer Recovery has mentioned to us about the Rehab program but we have no way to pay for it.
we have tried asking family members to help us out but tehy said the interest is too high and even if they helped us it would only remove the interest not the principle. Base on my situation is it possible that my family members can help us repay the principle and waive the interest?