This seems reasonable to me Cat.
Part of the problem that we have been experiencing regarding our national debt is that many have equated credit as a potential income and have been using it as such, thus driving themselves into further debt.
Right now the banks are tightening their belts. They were giving out loans loosely and recklessly without regards to the implications and the repercussions of these unsound practices that are now coming home to roost.
Basically they flooded the market with money and people were allowed to borrow this money backed by property which they did not own.
Your full potential debt includes any debt that you currently have AND and debt that you can easily gain. (Credit Cards)
Even if someone practices good financial tactics throughout their lives, if a time of extreme financial hardship comes about, the person, normally fueled by necessity, turns to credit such as loans if they can and or credit cards.
A person who is in dire straights is willing to fully max out all credit potential they possess and worry about the ramifications at another time...if they are able to get back on their feet.
The problem is compounded however by the fact that many times even if the person is able to get back to their feet, the payments required to pay for their debts are overwhelming, thus sending them into bankruptcy.
I'm not sure how many credit cards your brother and your wife have between them, nor how much credit available, but as a common practice, it is a good idea to only hold one credit card for each them which is used only in the case of an emergency and if at all possible to pay it off at the end of every month.
Just my 2 cents. I charge no interest