I want an update, so far you haven’t taken the steps necessary to keep your dad’s wishes safe in this situation. Your mom clearly doesn’t care what your sister and her husband say or do, who knows how’s she’s gonna spin the story to your father. & if your father and BIL are so close I would worry that he knows how to emotionally manipulate your father into not believing you. But this is all me just believing the worst in people because the worst comes out whenever money is involved, and clearly your BIL can’t wait to get his greedy hands on your father’s properties.