Do agricultural lands purchased with mixed funds (my grandfather's money and my grandmother's money, who suffers from Alzheimer's) fall under inheritance and are subject to division?

If two people own something together, the share of the deceased is distributed among their heirs. A partner's relinquishment of their right to their partner is permissible if done voluntarily, and it is considered a gift (hibah). The gift or financial transactions of an insane person are not valid due to their lack of legal capacity, unless they recover and regain their sanity, in which case their actions become valid. Therefore, if the grandmother relinquished her right to her husband while she was in full possession of her mental faculties, the relinquishment is valid, and the entire land enters into the inheritance. However, if her relinquishment occurred during her illness and lack of discernment, it is not valid, and her share remains her sole property, added to her right in the inheritance.