Unfortunately anyone may be sued over anything. However, if I understand the facts correctly it doesn't appear that there would be a basis for a lawsuit as your relative has the right to sell her interest in any property she owns. There may be additional facts that could give rise to a meritorious lawsuit; however, they aren't evident in the facts as presented.
While the upset family members may not have any valid basis to set aside the sale of the controlling share, they do have standing to file a Partition action. When there is more than one owner the court can be asked to either partition or sell the property. Not too complicated to partition if its a large enough tract and there are just 2 owners. Unfortunately, you have numerous owners with varying interests and it may prove impossible to partition the land. This would lead to a sale and the money would be divided according to the parties respective interests.
I have to agree with both Michael's above. Michael Y used my patent answer of YES before anyone finishes the sentence of "can I be sued over "....?
If you sold any land that involved an attorney title certification at closing then you I suspect you had a right to sell it unless there was some private contract that was not on the record.
Sounds like some form of corporation or family trust involved. See a real estate attorney and bring your paperwork.
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