Sale of ancestral property

A women has two sons and stays with her husband with one son. She has property given to her by her mother-in-law s brother. She has sold the said property to her son and a third person without consent or knowledge of other son. During the time of executing sale deed she was undergoing psychiatric treatment and was on antidepressant medication. Is the sale deed valid. Can it be revoked and the other son get his share in property. Please advise.