Mother-in-law Passed Away Right Before Closing

My husband's family has a piece of property that has been in the family for at least 60 years. His paternal grandfather built the houses, he's been going there his whole life, lived there for 30 years. It's a very special property to only him.

His dad passed away a couple years ago and his mom and siblings wanted to sell the property to pay for Mom and disabled sister's care. A day before the closing we found out there was I guess a judgment on the property for an unpaid ambulance bill. So that halted things. The next day Mom got sick and ended up passing on the 31st of December.

My husband does not want to sell this property but his sister is telling him that they will be sued for breach of contract if they don't go through with the sale. The buyer is a bulldog civil lawyer trying to buy up three blocks and this is the only structure in the way of her plans so she won't back down easily.

Does Mom passing change the situation to where a new contract would have to be drawn up anyway? Any and all advice as welcome as my husband is feeling pretty helpless and hopeless but I don't think it's a lost cause yet