Do they not have shares in the credit union. Also what exactly is their income, what are their outgoings, how much is the repayments, what are the terms of the loans and the interest rates?
A consolidated loan is what you are looking for and it's unlikely any bank will give this. But maybe they would if someone went guarantor. But this is a lot of debt (about 70K)
There used to be a product (insurance type policy) for retired people who had equity in their homes, like they sell the house to the bank, they keep the house and when they die the bank gets it's money. But one would need to be very careful with these.
Other option is for someone to take on the full 70K debt, get a loan from their bank and everybody pay it back. But that's messy, can lead to siblings fighting, and tricky issues if one of the parent's dies, gets ill etc. Also not advisable for someone to take on anothers debts when there is no guaranee of getting repaid.
Next option is Mabs, see if they can get the debt rescheduled so there is doable repayments.
Talking to the banks and credit unions to see what the options are.
Also the four of you could tackle the debt with the highest interest rate first. Pay that one first. Also the issue of why there are these debts has to be discussed, if it's the case that helping with the debt means your parents will apply for more credit, well then it's pointless helping them.