People who cannot swim are typically incapable of helping those who are drowning. Because of this I would encourage you and your siblings to get really good with finances. For this I would recommend Financial Peace University. It is a great primer on how to bring your financial house under control.
After this, you can help your parents appropriately. Setting boundaries and limits to the help you provide is a key to maintaining your own financial well being while also making sure they are taken care of. As people who have lived beyond their means during their working years it is likely to continue when they have more free time on their hands, increased medical costs, and a limited income. The fact they are considering retirement, while they have a large mortgage and no assets, indicates foolishness. You don't want to be sucked into that.
A person with first hand experience with this relayed a story. They were helping a related divorcee with a living situation, yet it was never enough. There was a breaking point that the older person wanted the younger couple to buy her a new car. Yet the car the older person was driving was newer then the husband or wife were driving. They were forced to set hard limits to the help they provided as without them they would have been driving into financial ruin themselves.
Seeking government or non-profit help will provide only minimalistic relief. Your goal would be for you to learn good financial habits, spread them to your siblings and children, and then attempt to help mom and dad. In other words learn how to swim!