Legal Question in Real Estate Law in Illinois

Insufficient information! You will need to see a trust/probate attorney who deals with residential real estate. That being said, if the house was in a trust, the trustee needs to take charge and work with the lender - maybe to refinance, or just bring the loan back out of default. If the property was not in a trust a probate estate needs to be opened (whether or not there's a will), and the executor will have to take charge (even if the will ultimately calls for the house to go into a "testamentary trust" (a trust set up in a will). Whichever is the situation, someone needs to act NOW as the property is already in foreclosure. The fact that your disabled sister lives in the house may create a "sympathy play" but that won't necessarily stop the lender. And depending on the disability, a guardianship may be needed to protect her interests.