He sold it without us knowing can he do that
This may be a case of elder abuse. You should talk to the Sheriff's Office.
It depends on what was signed, the mental condition of your mother, and how your brother obtained the alleged authority to sell. You will probably need a hired attorney to review the matter.
The sale is assumed to be valid. In order to set aside the sale, you will need to interdict your mother and be places in charge of her affairs. Then you have to file a lawsuit to set aside the sale.
Then questions arise as to can you get the property back, who pays, what about the attorney's fees?
This is way too complicated to answer in a quick answer - but short answer is yes, there are things you CAN do. Question is - is there enough money involved to justify an attorney involvement and what about future possible fraud?
If you don't consult an attorney, I would at least consider the elder abuse angle suggested above. They have advocacy groups to protect the elderly. My results with them have been sometimes very good, others not so much. But they generally do what they can. If they agree there has been abuse. Before contact them, be SURE that you have 100% "clean hands" - that you have not been receiving any money from Mom.
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