Officially it's none of your business, but morally and ethically it is.
After all, when they run out of credit, who do you think they will call? Their son, your husband.
When they lose their home, who do you think they will ask to let them live with them? That's right, your husband.
Have your husband ask his mom to hunt down their annual SSA earnings history and try to figure out what they will get in SSA benefits when they retire. That could well be their ONLY source of income when they stop working.
Then, seriously look at that amount and say, if they rented an apartment/mobile home, one car, food, etc, is this enough if they stick to a very tight budget? Could you and your siblings send them each $0/$100/$200 a month and stand firm?
The long and short of it is, they may end up with losing the house to foreclosure and going through bankruptcy to get rid of the credit card debt. (I hope they don't owe taxes, but even those can be postponed once they are living on just social security benefits.)
I would check www.daveramsey.com and see if there is a Financial Peace University class going on in their area and offer to pay for them to take the class. Buy them a copy of Total Money Makeover and give it to them. Dave has a mantra that you CANNOT earn your way out of debt.
I was an accountant for many years. I've seen this scenario more times that I can count. It is a spend first, ask questions later mentality. People who are impulse buyers get into this trap. There is very little you can do to help them, unfortunately.
Dave Ramsey for the win! His CDs have changed my life and the lives of my parents.
Welcome to America, the land of opportunity!
It is none of your business.