What is the Sharia ruling if a woman asks her brothers not to give her inheritance money (which they are holding for her) to her husband or her husband's family after her death, due to her distrust of them and her concern that they may not spend it on her son?

A woman is permitted to entrust her money to her brothers for safekeeping and investment during her lifetime. However, she is not permitted to stipulate that it be withheld from anyone after her death, because upon death, the money ceases to be her property and becomes the inheritance of her heirs. She does not have the right to withhold it from them, unless she bequeaths one-third or less of it to someone who is not an heir. For example, if she bequeaths it to the poor, the needy, and other charitable causes, this is permissible and is a charity that increases her good deeds after her death, in accordance with the Prophet's (peace and blessings be upon him) saying: "Indeed, Allah has bestowed upon you, at the time of your death, a third of your wealth as an increase for you in your deeds."