Is claiming the widow's and her children's share of land registered in the name of the deceased husband permissible (halal) or forbidden (haram), especially if the ownership of the land goes back to the husband's father who registered it in his son's name due to special circumstances, and what is the ruling of Islamic law on the widow's insistence on her right to this land despite the demands of the husband's family for her to relinquish it?

A person's estate after their death is distributed among their heirs after debts are paid and bequests are executed. Land registered in the husband's name and in his possession is outwardly considered his property. The brothers' claim that the land belongs to the husband's father requires evidence, based on the Prophet's (peace be upon him) saying: "The burden of proof is on the claimant, and the oath is on the one who denies." If they do not have evidence and you do not believe their claim, you are not obligated to waive your share. As for the share of your minor children, it is not permissible to waive it except with evidence that proves the claim of the husband's family. This matter requires a Sharia (definition) court.